docs: def get_beam(secret_uuid):
      """
      Get a beam from the session with `secret_uuid`.
  
      Parameters
      ----------
      secret_uuid : str
  
      Returns
      -------
      The beam object if it exists, otherwise `None`.
      """
      beam_dir = get_beam_cache_directory()
      beam_filename = os.path.join(beam_dir, secret_uuid)
      if os.path.isfile(beam_filename):
          with open(beam_filename, 'rb') as handle:
              beam = pickle.load(handle)
          return beam
      else:
          return None