def is_nucleus(particle):
    """Test if particle is a nucleus.

    See dataclasses/private/dataclasses/physics/I3Particle.cxx

    Parameters
    ----------
    particle : shape () ndarray of dtype I3PARTICLE_T

    Returns
    -------
    is_nucleus : bool

    """
    return 1000000000 <= abs(particle["pdg_encoding"]) <= 1099999999