def atom_num_radical_electrons(atom):
    """Get the number of radical electrons for an atom.

    Parameters
    ----------
    atom : rdkit.Chem.rdchem.Atom
        RDKit atom instance.

    Returns
    -------
    list
        List containing one int only.

    See Also
    --------
    atom_num_radical_electrons_one_hot
    """
    return [atom.GetNumRadicalElectrons()]
