code: def _extract_schema_if_given(table_name):
      
      pattern = '^(([^.]+)\.)?(.+)$'
      m = re.match(pattern, table_name)
      schema, table_name = m.group(2), m.group(3)
      return schema, table_name
docs: Return a pair (schema, table) derived from the given `table_name`
      (anything before the first '.' if the name contains one; otherwise
      the return value of `schema` is None).
  
      Examples:
  
          >>> _extract_schema_if_given('some_schema.my_table')
          ('some_schema', 'my_table')
  
          >>> _extract_schema_if_given('my_awesome_table')
          (None, 'my_awesome_table')