code: def peek(self, fmt):
          
          pos_before = self._pos
          value = self.read(fmt)
          self._pos = pos_before
          return value
docs: Interpret next bits according to format string and return result.
  
          fmt -- Token string describing how to interpret the next bits.
  
          The position in the bitstring is not changed. If not enough bits are
          available then all bits to the end of the bitstring will be used.
  
          Raises ReadError if not enough bits are available.
          Raises ValueError if the format is not understood.
  
          See the docstring for 'read' for token examples.