def find_all_starts(seq):
    """Find the starting index of all start codons in a lowercase seq"""
    # Initialize array of indices of start codons
    starts = []

    # Find index of first start codon (remember, find() returns -1 if not found)
    i = seq.find('atg')

    # Keep looking for subsequence incrementing starting point of search
    while i >= 0:
        starts.append(i)
        i = seq.find('atg', i + 1)

    return tuple(starts)