code: def evaluate(self, source):
  		
  		ret = self.check(source)
  		if self._neg:
  			ret = not ret
  		if ret:
  			if self._if:
  				return self._if
  		elif self._else:
  			return self._else
docs: Evaluates the board state from `source` and returns an iterable of
  		Actions as a result.