docs: def save(self):
          """
          Update the SouceReading information for the currently recorded observations and then flush those to a file.
          @return: mpc_filename of the resulting save.
          """
          self.get_writer().flush()
          mpc_filename = self.get_writer().get_filename()
          self.get_writer().close()
          self._writer = None
          return mpc_filename