dataframe value changed after inserted to Decimal() type column using insert_dataframe() method

[zsmeijin]

Describe the bug
dataframe value changed after insert to Decimal() type column using insert_dataframe() method.
In Class DecimalColumn method before_write_items, value is scaled before inserted, it seems done by reference and scales dataframe column's value directly. it is confusing to have dataframe's value changed without notice

    def before_write_items(self, items, nulls_map=None):
        null_value = self.null_value

        if self.scale >= 1:
            scale = 10 ** self.scale

            for i, item in enumerate(items):
                if nulls_map and nulls_map[i]:
                    items[i] = null_value
                else:
                    items[i] = int(Decimal(str(item)) * scale)

        else:
            for i, item in enumerate(items):
                if nulls_map and nulls_map[i]:
                    items[i] = null_value
                else:
                    items[i] = int(Decimal(str(item)))

To Reproduce
create a table contains Decimal column, and using insert_dataframe() insert a dataframe

Expected behavior
dataframe unchanged after insert

Versions
package version: 0.2.2
python version: 3.8.9