code: def masked_neighborhoods(self,seq,flanksize):
          
          ns = self.seq_neighborhoods(seq,flanksize)
          return [self.mask_seq(n) for n in ns]
docs: m.masked_neighborhoods(seq,flanksize) -- Chop up the input sequence into regions surrounding matches to m.  Replace the
                                                   subsequences that match the motif with N's.