Add get_column_names method to metadata

[frances-h]

Problem Description

As a user, I'd like to be able to easily get a list of all the column names in my metadata that meet the given criteria. For example, after, automatically detecting my metadata I'd like to be able to get a list of all of the columns that have the sdtype unknown

Expected behavior

Add a method get_column_names that takes in metadata keyword arguments and returns a list of all the column names that match those arguments

Single Table API

• get_column_names(**metadata_kwargs)
  • **metadata_kwargs - Metadata keyword arguments to use to filter columns. If no kwargs are passed, all column names should be returned. Otherwise, should only return the list of column names in the metadata that match the provided kwargs.

metadata = SingleTableMetadata.detect_from_dataframe(data)
unknown_cols = metadata.get_column_names(sdtype='unknown')

Multi Table API

• get_column_names(table_name, **metadata_kwargs)
  • table_name (str) - the name of the target table
  • **metadata_kwargs - Metadata keyword arguments to use to filter columns. If no kwargs are passed, all column names should be returned. Otherwise, should only return the list of column names in the metadata that match the provided kwargs.

metadata = MultiTableMetadata.detect_from_dataframes(data)
unknown_cols = metadata.get_column_names('table1', sdtype='unknown')