docs: def _parse_version_string(version_conditions_string):
      '''
      Returns a list of two-tuples containing (operator, version).
      '''
      result = []
      version_conditions_string = version_conditions_string.strip()
      if not version_conditions_string:
          return result
      for version_condition in version_conditions_string.split(','):
          operator_and_version = _get_comparison_spec(version_condition)
          result.append(operator_and_version)
      return result