def METHOD_NAME(self):
    """
    Method called if aperture, slits or focusing has been changed
    Returns: dictionary, {size_x: 0.1, size_y: 0.1, shape: BeamShape enum}
    """
    size_x = min(
        self._beam_size_dict["aperture"][0], self._beam_size_dict["slits"][0]
    )
    size_y = min(
        self._beam_size_dict["aperture"][1], self._beam_size_dict["slits"][1]
    )
    self._beam_width = size_x
    self._beam_height = size_y
    if tuple(self._beam_size_dict["aperture"]) < tuple(
        self._beam_size_dict["slits"]
    ):
        self._beam_shape = BeamShape.ELIPTICAL
    else:
        self._beam_shape = BeamShape.RECTANGULAR
    self._beam_info_dict["size_x"] = size_x
    self._beam_info_dict["size_y"] = size_y
    self._beam_info_dict["shape"] = self._beam_shape
    return self._beam_info_dict