def validate_codons(starts,stops):
    """
    Check if codons are valid

    Parameters
    ----------
    starts : list
        List of start codons.
    stops : list
        List of stop codons.

    Returns
    -------
    bool
        True is codons are fine.

    """
    validalphabets=['A','C','T','G']
    if not starts:
        starts=[]
    if not stops:
        stops=[]
    #check lengths
    for c in starts:
        if not len(c)==3:
            print('Invalid start codon:'+c)
            return False
        if not ((c[0] in validalphabets) and (c[1] in validalphabets) and (c[2] in validalphabets)):
            print('Invalid start codon:'+c)
            return False
    for c in stops:
        if not len(c)==3:
            print('Invalid stop codon:'+c)
            return False
    #check intersection
    for c in starts:
        if c in stops:
            print('Invalid codon in both lists:'+c)
            return False
    return True