code: def window(featurestream, seqid, start=None, end=None, strict=True):
      
      region = None
      if start and end:
          region = tag.Range(start, end)
  
      for feature in featurestream:
          if feature.seqid != seqid:
              continue
          if region:
              if strict:
                  if region.contains(feature._range):
                      yield feature
              else:
                  if region.overlap(feature._range):
                      yield feature
          else:
              yield feature
docs: Pull features out of the designated genomic interval.
  
      This function uses 0-based half-open intervals, not the 1-based closed
      intervals used by GFF3.
  
      :param featurestream: a stream of feature entries
      :param seqid: ID of the sequence from which to select features
      :param start: start of the genomic interval
      :param end: end of the genomic interval
      :param strict: when set to :code:`True`, only features completely contained
                     within the interval are selected; when set to :code:`False`,
                     any feature overlapping the interval is selected