def has_no_overlap(r1, r2):
    """Returns True if the two reads overlap.
    """
    r1_start, r1_end = r1.reference_start, r1.reference_end
    r2_start, r2_end = r2.reference_start, r2.reference_end
    return r2_end <= r1_start or r1_end <= r2_start
