diff --git a/transformers/hierarchical/ParallelGroupPrevDays.py b/transformers/hierarchical/ParallelGroupPrevDays.py
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+++ b/transformers/hierarchical/ParallelGroupPrevDays.py
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+# Purpose: For transactional grouped data, calculate historical percentage of the target value
+#
+# Expected ML Problem: Transactional binary classification for many groups
+# Example Use Cases: part failure, credit card fraud
+# Overview: Takes hardcoded groups and time
+#
+# DAI Version: 1.8.0
+# Important Note: Models with this transformer should be retrained frequently
+
+
+from h2oaicore.transformer_utils import CustomTransformer
+import datatable as dt
+import numpy as np
+import pandas as pd
+from datetime import timedelta
+from h2oaicore.systemutils import (
+    small_job_pool, save_obj, load_obj, temporary_files_path, remove, max_threads, config,
+    make_experiment_logger, loggerinfo, loggerwarning
+)
+import os
+import uuid
+import shutil
+import joblib
+
+
+# Parallel implementation requires methods being called from different processes
+# Global methods support this feature
+# We use global methods as a wrapper for member methods of the transformer
+def transformer_fit_transform_async(*args, **kwargs):
+    return ParallelPCTDaysTransformer._fit_transform_async(*args, **kwargs)
+
+
+class ParallelPCTDaysTransformer(CustomTransformer):
+    # only for binary classification
+    _regression = False
+    _binary = True
+    _multiclass = False
+
+    _numeric_output = True
+    _is_reproducible = True
+    _included_model_classes = None
+    _excluded_model_classes = None
+
+    # give easy-to-understand names in the UI
+    _allow_transform_to_modify_output_feature_names = True
+
+    # Allow transformer to be used by DAI
+    @staticmethod
+    def is_enabled():
+        return True
+
+    # Cannot use DAI code testing as we have hard coded column names
+    @staticmethod
+    def do_acceptance_test():
+        return False
+
+    # Requires all columns in the data set
+    @staticmethod
+    def get_default_properties():
+        return dict(col_type="all", min_cols="all", max_cols="all", relative_importance=1)
+
+    # Set the hard coded values about our data set
+    def __init__(self, **kwargs):
+        super().__init__(**kwargs)
+        self.col_date = "event_ts"
+        self.col_group = ["customer_id"]
+        self.target_positive = "Yes"
+
+        # the number of DAYS or Rows we want to look back
+        self.timespans = [30, 60, 90]
+
+    # This function runs during training
+    def fit_transform(self, X: dt.Frame, y: np.array = None, **kwargs):
+
+        # Get logger, create temp folder for parallel processing
+        # and get number of workers allocated to the transformer
+        logger = self.get_experiment_logger()
+        tmp_folder = self._create_tmp_folder(logger)
+        n_jobs = self._get_n_jobs(logger, **kwargs)
+
+        # values we need to accessible in other parts of DAI
+        features = []
+        self._output_feature_names = []
+        self._feature_desc = []
+
+        # list of group by and time columns
+        cols_agg = self.col_group.copy()
+        cols_agg.append(self.col_date)
+
+        # list of group by, time, and y columns
+        cols_agg_y = cols_agg.copy()
+        cols_agg_y.append('col_target_bin')
+
+        # Move to pandas
+        # Pandas index is no 0 to len X - 1
+        X = X.to_pandas()
+
+        # Make a 0/1 column for if the event happened or not
+        X['col_target_bin'] = (y == self.target_positive).astype(int)
+
+        # Make sure time is time
+        X[self.col_date] = pd.to_datetime(X[self.col_date])
+
+        # We need to sort by date then groupby customer_id and finally shift 1 event
+        X = X.sort_values(self.col_date)
+        X['col_target_bin'] = X.groupby(self.col_group)['col_target_bin'].shift(1).fillna(0)
+        # Go back to original index
+        X.sort_index(inplace=True)
+
+        # Create a feature for each of the requested days / rows
+        # Initialize the feature result with index set, this way features are added in correct row order even
+        # if feature comes out with an unordered index
+        feats_df = pd.DataFrame(index=X.index)
+        for t in self.timespans:
+            # Create feature name
+            t_days = str(t) + "d"  # use t instead of t_days if you want to aggregate by rows - other units of time can be used as well
+            # Create the groups
+            groups = X[cols_agg_y].groupby(self.col_group)
+
+            # prepare parallel processing
+            df_paths = []
+
+            def processor(out, res):
+                out.append(res)
+
+            num_tasks = len(groups)
+            pool_to_use = small_job_pool
+            pool = pool_to_use(
+                logger=None, processor=processor,
+                num_tasks=num_tasks, max_workers=n_jobs)
+
+            # Go though the groups and predict only top
+            feat_list = []
+            for _key, _df in groups:
+                # Sort the group by date, this is required for the rolling per time interval to work
+                _df = _df.sort_values(self.col_date)
+                # Create path for storage
+                a_path = os.path.join(tmp_folder, "grp_prev_dev_df" + str(uuid.uuid4()))
+                # Store frame
+                save_obj(_df, a_path)
+                # Prepare arguments to be passed to the fit transform method
+                args = (a_path, self.col_date, t_days, tmp_folder)
+                kwargs = {}
+                # Add to the pool
+                pool.submit_tryget(
+                    logger=None,
+                    function=transformer_fit_transform_async,
+                    args=args, kwargs=kwargs,
+                    out=df_paths  # df_paths will receive the path where job results are stored
+                )
+
+            # Now that the jobs have been processed
+            # Concat group results and assign to result dataframe
+            # Since dataframe is indexed, feature is inluded in the appropriate row_order
+            # i.e. pandas make sure index on both sides agree
+            pool.finish()
+            feats_df[t_days] = pd.concat((load_obj(a_path) for a_path in df_paths), axis=0)
+
+            for p in df_paths:
+                remove(p)
+
+            # Set the column names and descriptions
+            self._output_feature_names.append("Y%: " + t_days)
+            self._feature_desc.append("Percent of Target with Event in Last " + str(t) + " Days")
+
+        # keep the max days needed of transactions for each person to look up in transform
+        time_filter = (
+            X[cols_agg].groupby(self.col_group)[self.col_date].transform('max') - X[self.col_date]
+        ) <= timedelta(days=max(self.timespans))
+
+        self.lookup_df = X.loc[time_filter].sort_values(self.col_date)
+
+        # Clean temp folder before exiting fit_transform
+        self._clean_tmp_folder(logger, tmp_folder)
+
+        # return the features
+        return feats_df
+
+    @staticmethod
+    def _fit_transform_async(df_path, col_date, t_days, tmp_folder):
+        # Load data
+        _df = load_obj(df_path)
+        # Apply rolling window but make sure target does not contain any NaN
+        res = _df.set_index(col_date)['col_target_bin'].fillna(0).rolling(t_days, min_periods=1).mean()
+        # It is not an apply and index may not be the original one
+        # Therefore make sure the index is the original one
+        res.index = _df.index
+        # Store result
+        res_path = os.path.join(tmp_folder, "grp_prev_days_res_df" + str(uuid.uuid4()))
+        save_obj(res, res_path)
+        remove(df_path)  # remove to indicate success
+        return res_path
+
+    # This function runs during scoring - it will look to what happened in the training data, so may get stale fast
+    # If we see a new customer we return 0 for the features, as there are no key events in their past
+    # It is also used to transform the validation set,
+    # which means validation set must be after (time wise) the training set
+    def transform(self, X: dt.Frame, **kwargs):
+
+        # Get logger, create temp folder for parallel processing
+        # and get number of workers allocated to the transformer
+        logger = self.get_experiment_logger()
+        tmp_folder = self._create_tmp_folder(logger)
+        n_jobs = self._get_n_jobs(logger, **kwargs)
+
+        # group by and time
+        cols_agg = self.col_group.copy()
+        cols_agg.append(self.col_date)
+
+        # group by, time, and y
+        cols_agg_y = cols_agg.copy()
+        cols_agg_y.append('col_target_bin')
+
+        # pandas
+        X = X.to_pandas()
+        original_index = X.index
+
+        # Make sure time is time
+        X[self.col_date] = pd.to_datetime(X[self.col_date])
+
+        # combine rows from training and new rows, col_target_bin will be null in new data
+        lkup_and_test = pd.concat([self.lookup_df, X], axis=0, sort=False).reset_index()
+
+        feats_df = pd.DataFrame(index=lkup_and_test.index)
+        for t in self.timespans:
+            # Create feature name
+            t_days = str(t) + "d"
+            # Create the groups
+            groups = lkup_and_test[cols_agg_y].groupby(self.col_group)
+
+            # prepare parallel processing
+            df_paths = []
+
+            def processor(out, res):
+                out.append(res)
+
+            num_tasks = len(groups)
+            pool_to_use = small_job_pool
+            pool = pool_to_use(
+                logger=None, processor=processor,
+                num_tasks=num_tasks, max_workers=n_jobs)
+
+            # Run through groups
+            feat_list = []
+            for _key, _df in groups:
+                # Sort the group by date, this is required for the rolling per time interval to work
+                _df = _df.sort_values(self.col_date)
+                # Create path for storage
+                a_path = os.path.join(tmp_folder, "grp_prev_days_df" + str(uuid.uuid4()))
+                # Store frame
+                save_obj(_df, a_path)
+                # Prepare arguments to be passed to the fit transform method
+                args = (a_path, self.col_date, t_days, tmp_folder)
+                kwargs = {}
+                # Add to the pool
+                pool.submit_tryget(
+                    logger=None,
+                    function=transformer_fit_transform_async,
+                    args=args, kwargs=kwargs,
+                    out=df_paths  # df_paths will receive the path where job results are stored
+                )
+
+                # Now that the jobs have been processed
+                # Concat group results and assign to result dataframe
+                # Since dataframe is indexed, feature is inluded in the appropriate row_order
+                # i.e. pandas make sure index on both sides agree
+            pool.finish()
+            feats_df[t_days] = pd.concat((load_obj(a_path) for a_path in df_paths), axis=0)
+
+            for p in df_paths:
+                remove(p)
+
+        # Only return rows whose index is below self.lookup_df size
+        feats_df = feats_df.loc[self.lookup_df.shape[0]:]
+        feats_df.index = original_index
+
+        # Clean temp folder before exiting fit_transform
+        self._clean_tmp_folder(logger, tmp_folder)
+
+        return feats_df
+
+    def get_experiment_logger(self):
+        logger = None
+        if self.context and self.context.experiment_id:
+            logger = make_experiment_logger(
+                experiment_id=self.context.experiment_id,
+                tmp_dir=self.context.tmp_dir,
+                experiment_tmp_dir=self.context.experiment_tmp_dir
+            )
+        return logger
+
+    def _create_tmp_folder(self, logger):
+        # Create a temp folder to store files used during multi processing experiment
+        # This temp folder will be removed at the end of the process
+        # Set the default value without context available (required to pass acceptance test
+        tmp_folder = os.path.join(temporary_files_path, "%s_grp_prev_days_folder" % uuid.uuid4())
+        # Make a real tmp folder when experiment is available
+        if self.context and self.context.experiment_id:
+            tmp_folder = os.path.join(self.context.experiment_tmp_dir, "%s_grp_prev_days_folder" % uuid.uuid4())
+
+        # Now let's try to create that folder
+        try:
+            os.mkdir(tmp_folder)
+        except PermissionError:
+            # This not occur so log a warning
+            loggerwarning(logger, "Transformer was denied temp folder creation rights")
+            tmp_folder = os.path.join(temporary_files_path, "%s_grp_prev_days_folder" % uuid.uuid4())
+            os.mkdir(tmp_folder)
+        except FileExistsError:
+            # We should never be here since temp dir name is expected to be unique
+            loggerwarning(logger, "Transformer temp folder already exists")
+            tmp_folder = os.path.join(self.context.experiment_tmp_dir, "%s_grp_prev_days_folder" % uuid.uuid4())
+            os.mkdir(tmp_folder)
+        except:
+            # Revert to temporary file path
+            tmp_folder = os.path.join(temporary_files_path, "%s_grp_prev_days_folder" % uuid.uuid4())
+            os.mkdir(tmp_folder)
+
+        loggerinfo(logger, "Transformer temp folder {}".format(tmp_folder))
+        return tmp_folder
+
+    def _clean_tmp_folder(self, logger, tmp_folder):
+        try:
+            shutil.rmtree(tmp_folder)
+            loggerinfo(logger, "Transformer cleaned up temporary file folder.")
+        except:
+            loggerwarning(logger, "Transformer could not delete the temporary file folder.")
+
+    @staticmethod
+    def _get_n_jobs(logger, **kwargs):
+        try:
+            if config.fixed_num_folds <= 0:
+                n_jobs = max(1, int(int(max_threads() / min(config.num_folds, kwargs['max_workers']))))
+            else:
+                n_jobs = max(1, int(
+                    int(max_threads() / min(config.fixed_num_folds, config.num_folds, kwargs['max_workers']))))
+
+        except KeyError:
+            loggerinfo(logger, "Transformer No Max Worker in kwargs. Set n_jobs to 1")
+            n_jobs = 1
+
+        loggerinfo(logger, f"Transformer n_jobs {n_jobs}")
+
+        return n_jobs
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