def revc(seq_string):
    """
    Return the reverse compelement of given nucleotide sequence
    """
    o = 'ACGTUWSMKRYBDHVNZacgtuwsmkrybdhvnz-'
    c = 'TGCAAWSKMYRVHDBNZtgcaawskmyrvhdbnz-'
    if len(set(seq_string) & set(o)) > len(set(seq_string)):
        errmsg = 'invalid character was found in the sequeces'
        raise RuntimeWarning(errmsg)
    return seq_string.translate(str.maketrans(o, c))[::-1]
