code: def get_nonmatching_blocks(matching_blocks):
      
      i = j = 0
      for match in matching_blocks:
          a, b, size = match
          yield (i, a, j, b)
          i = a + size
          j = b + size
docs: Given a list of matching blocks, output the gaps between them.
  
      Non-matches have the format (alo, ahi, blo, bhi). This specifies two index
      ranges, one in the A sequence, and one in the B sequence.