code: def as_file(self):
          
          use_data_if_no_file = not self._file and self._data
          if use_data_if_no_file:
              if self._base64_file_content:
                  if isinstance(self._data, str):
                      content = self._data.encode()
                  else:
                      content = self._data
                  self._file = _create_temp_file_with_content(
                      base64.standard_b64decode(content))
              else:
                  self._file = _create_temp_file_with_content(self._data)
          if self._file and not os.path.isfile(self._file):
              raise ConfigException("File does not exists: %s" % self._file)
          return self._file
docs: If obj[%data_key_name] exists, return name of a file with base64
          decoded obj[%data_key_name] content otherwise obj[%file_key_name].