docs: def add_artifact(self, artifact):
          '''Add artifact with given framing to the environment.
  
          :param object artifact: Artifact to be added.
          '''
          artifact.env_time = self.age
          self.artifacts.append(artifact)
          self._log(logging.DEBUG, "ARTIFACTS appended: '{}', length={}"
                    .format(artifact, len(self.artifacts)))