def get_labels(ss):
    """Return two labels from a string containing "-" or two words starting with a capital.

    For example, the input string may be 'G-X', 'GX', 'Gamma-X', 'GammaX'.
    The output is always: ('G', 'X') or ('Gamma', 'X').
    """
    if '-' in list(ss):
        labels = ss.split('-')
    else:
        lss = list(ss)
        ixs = [i for i,c in enumerate(lss) if c != c.lower()]
        assert len(ixs) == 2, ixs
        assert ixs[0] == 0, ixs
        labels = [''.join(lss[:ixs[1]]), ''.join(lss[ixs[1]:])]
    return labels