def __init__(self, n_electrons=None, zenith=None, azimuth=None, s1=None,
                 s2=None):
        if n_electrons is not None:
            self._n_electrons = n_electrons
        if zenith is not None:
            self._zenith = zenith
        if azimuth is not None:
            self._azimuth = azimuth
        if s1 is not None:
            self._s1 = s1
        if s2 is not None:
            self._s2 = s2

        self._cache_c_s_value()