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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def evaluate(self, source):
 		""" 		Evaluates the board state from `source` and returns an iterable of 		Actions as a result. 		"""

		ret = self.check(source)
		if self._neg:
			ret = not ret
		if ret:
			if self._if:
				return self._if
		elif self._else:
			return self._else