def EnumerateRingBond(mol, idxlist):
    """
    Enumerate bonds in a cycle

    Input:

    mol: rdMol

    idxlist: list (ring atoms)

    Return:

    ringbond: list of tuples [(atom_1, atom_2)]
    
    """
    ringbond = []
    size = len(idxlist)
    ringbond = [(idxlist[i%size],idxlist[(i+1)%size]) for i in range(size)]
    return ringbond