Get a beam from the session with `secret_uuid`.

    Parameters
    ----------
    secret_uuid : str

    Returns
    -------
    The beam object if it exists, otherwise `None`.

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