def METHOD_NAME(region_tups):
    """Drop contigs with noncanonical names.
    `region_tups` is an iterable of (chrom, start, end) tuples.
    Yield the same, but dropping noncanonical chrom.
    """
    # Avoid a circular import
    from .antitarget import is_canonical_contig_name
    return (tup for tup in region_tups if is_canonical_contig_name(tup[0]))