def feat_overlap(f1, f2):
    """
    Given two features (lists of length=9 from GFF3), determine whether they
    overlap.
    """
    f1start = int(f1[3])
    f1end = int(f1[4])
    f2start = int(f2[3])
    f2end = int(f2[4])

    if f1start <= f2end and f1end >= f2start:
        return True
    return False