code: def add_metadata(self, observation_n, info_n, available_at=None):
          
          if self.instance_n is None:
              return
  
          with pyprofile.push('vnc_env.diagnostics.Diagnostics.add_metadata'):
              async = self.pool.imap_unordered(
                  self._add_metadata_i,
                  zip(self.instance_n, observation_n, info_n, [available_at] * len(observation_n)))
              list(async)
docs: Mutates the info_n dictionary.