docs: def replace_missing_value(self, str_in):
          # type: (Text) -> Text
          """ returns 'str_in' if it is not equals to the 'sentinel' as
          defined in the missingValue section of
          the schema. Else it will return the 'replaceWith' value.
  
          :param str_in:
          :return: str_in or the missingValue replacement value
          """
          if self.missing_value is None:
              return str_in
          elif self.missing_value.sentinel == str_in:
              return self.missing_value.replace_with
          else:
              return str_in