code: def parse_select(cls, text: str) -> Set:
          
          if text == '*':
              return ALL_COLUMNS  # None means ALL
          selected_columns = set(filter(lambda x: x, map(str.strip, text.split(','))))
          if not selected_columns:
              raise InvalidParams("No column(s) selected")
          return selected_columns
docs: get columns from select text
          :param text: col1, col2
          :return: ALL_COLUMNS or ['col1', 'col2']