def find_indels(ref_aln, qry_aln):
    """
    Identify the positions of indels in the alignment of 2 sequences
    
    :param ref_aln: An aligned sequence representing the reference
    :param qry_aln: An aligned sequence representing the query
    :yields:        The position of each gap character in the alignment
    """
    assert len(ref_aln) == len(qry_aln
        ), 'Error - Aligned sequence lengths do not match'
    for pos, pair in enumerate(zip(ref_aln, qry_aln)):
        if '-' in pair:
            yield pos
