code: def sequence(self, fasta, use_strand=True):
          
          if isinstance(fasta, six.string_types):
              fasta = Fasta(fasta, as_raw=False)
  
          # recall GTF/GFF is 1-based closed;  pyfaidx uses Python slice notation
          # and is therefore 0-based half-open.
          seq = fasta[self.chrom][self.start-1:self.stop]
          if use_strand and self.strand == '-':
              seq = seq.reverse.complement
          return seq.seq
docs: Retrieves the sequence of this feature as a string.
  
          Uses the pyfaidx package.
  
          Parameters
          ----------
  
          fasta : str
              If str, then it's a FASTA-format filename; otherwise assume it's
              a pyfaidx.Fasta object.
  
          use_strand : bool
              If True (default), the sequence returned will be
              reverse-complemented for minus-strand features.
  
          Returns
          -------
          string