code: def format_seq(self, outstream=None, linewidth=70):
          
          if linewidth == 0 or len(self.seq) <= linewidth:
              if outstream is None:
                  return self.seq
              else:
                  print(self.seq, file=outstream)
                  return
  
          i = 0
          seq = ''
          while i < len(self.seq):
              if outstream is None:
                  seq += self.seq[i:i+linewidth] + '\n'
              else:
                  print(self.seq[i:i+linewidth], file=outstream)
              i += linewidth
          if outstream is None:
              return seq
docs: Print a sequence in a readable format.
  
          :param outstream: if `None`, formatted sequence is returned as a
                            string; otherwise, it is treated as a file-like
                            object and the formatted sequence is printed to the
                            outstream
          :param linewidth: width for wrapping sequences over multiple lines; set
                            to 0 for no wrapping