[SDK/CLI] Hide internal constants (#552)

# Description

Please add an informative description that covers that changes made by
the pull request and link all relevant issues.

# All Promptflow Contribution checklist:
- [ ] **The pull request does not introduce [breaking changes]**
- [ ] **CHANGELOG is updated for new features, bug fixes or other
significant changes.**
- [ ] **I have read the [contribution guidelines](../CONTRIBUTING.md).**

## General Guidelines and Best Practices
- [ ] Title of the pull request is clear and informative.
- [ ] There are a small number of commits, each of which have an
informative message. This means that previously merged commits do not
appear in the history of the PR. For more information on cleaning up the
commits in your PR, [see this
page](https://github.com/Azure/azure-powershell/blob/master/documentation/development-docs/cleaning-up-commits.md).

### Testing Guidelines
- [ ] Pull request includes test coverage for the included changes.

docs/dev/documentation_guidelines.md

@@ -95,6 +95,7 @@ class MyClass:
     - Single backticks (`): Single backticks are used to represent inline code elements within the text. It is typically used to highlight function names, variable names, or any other code elements within the documentation.
     - Double backticks(``): Double backticks are typically used to highlight a literal value.
 
+8. If there are any class level constants you don't want to expose to doc site, make sure to add `_` in front of the constant to hide it.
 
 ### Write function docstring
 

src/promptflow/promptflow/azure/operations/_run_operations.py

@@ -73,8 +73,9 @@ class RunOperations(_ScopeDependentOperations):
     attaches it as an attribute.
     """
 
-    DATASTORE_PATH_PATTERN = re.compile(r"azureml://datastores/(?P<datastore>[\w/]+)/paths/(?P<path>.*)$")
-    ASSET_ID_PATTERN = re.compile(r"azureml:/.*?/data/(?P<name>.*?)/versions/(?P<version>.*?)$")
+    # add "_" in front of the constant to hide them from the docstring
+    _DATASTORE_PATH_PATTERN = re.compile(r"azureml://datastores/(?P<datastore>[\w/]+)/paths/(?P<path>.*)$")
+    _ASSET_ID_PATTERN = re.compile(r"azureml:/.*?/data/(?P<name>.*?)/versions/(?P<version>.*?)$")
 
     def __init__(
         self,
@@ -131,7 +132,7 @@ def _get_input_portal_url_from_input_uri(self, input_uri):
             return None
         if input_uri.startswith("azureml://"):
             # input uri is a datastore path
-            match = self.DATASTORE_PATH_PATTERN.match(input_uri)
+            match = self._DATASTORE_PATH_PATTERN.match(input_uri)
             if not match or len(match.groups()) != 2:
                 logger.warning(error_msg)
                 return None
@@ -156,7 +157,7 @@ def _get_portal_url_from_asset_id(self, output_uri):
         error_msg = f"Failed to get portal url: {output_uri!r} is not a valid azureml asset id."
         if not output_uri:
             return None
-        match = self.ASSET_ID_PATTERN.match(output_uri)
+        match = self._ASSET_ID_PATTERN.match(output_uri)
         if not match or len(match.groups()) != 2:
             logger.warning(error_msg)
             return None