def _check_soma_topology_swc(points):
    '''check if points form valid soma

    Currently checks if there are bifurcations within a soma
    with more than three points.
    '''
    if len(points) == 3:
        return

    parents = tuple(p[COLS.P] for p in points if p[COLS.P] != ROOT_ID)
    if len(parents) > len(set(parents)):
        raise SomaError("Bifurcating soma")
check if points form valid soma

    Currently checks if there are bifurcations within a soma
    with more than three points.