code: def sense(self):
          
          haystack = bitstrings.BitString.random(self.input_size)
          self.needle_value = haystack[self.needle_index]
          return haystack
docs: Return a situation, encoded as a bit string, which represents
          the observable state of the environment.
  
          Usage:
              situation = scenario.sense()
              assert isinstance(situation, BitString)
  
          Arguments: None
          Return:
              The current situation.