docs: def genome_alignment_iterator(fn, reference_species, index_friendly=False,
                                verbose=False):
    """
    build an iterator for an MAF file of genome alignment blocks.
  
    :param fn:                 filename or stream-like object to iterate over.
    :param reference_species:  which species in the alignment should be treated
                               as the reference?
    :param index_friendly:     if True, buffering is disabled to support using
                               the iterator to build an index.
  
    :return an iterator that yields GenomeAlignment objects
    """
    kw_args = {"reference_species": reference_species}
    for e in maf.maf_iterator(fn, index_friendly=index_friendly,
                              yield_class=GenomeAlignmentBlock,
                              yield_kw_args=kw_args,
                              verbose=verbose):
      yield e