def _get_c_of_mass(rdmol):
    """
    Get the unweighted centre of mass of an RDKit Molecule
    :param rdmol:
    :return:
    """
    atoms = rdmol.GetAtoms()
    conf = rdmol.GetConformer()
    x_coord = y_coord = z_coord = 0.0
    numatoms = 0.0
    for atom in atoms:
        if atom.GetAtomicNum() == 1 or atom.GetSmarts() == '[*]':
            continue
        numatoms += 1.0
        coords = conf.GetAtomPosition(atom.GetIdx())
        x_coord += float(coords.x)
        y_coord += float(coords.y)
        z_coord += float(coords.z)
    if numatoms == 0:
        raise ValueError('No atoms in Molecules')
    return x_coord / numatoms, y_coord / numatoms, z_coord / numatoms
