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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 eval(self, construct):
 """Evaluate an expression returning its value. The Python equivalent of the CLIPS eval command. """

        data = clips.data.DataObject(self._env)

        if lib.EnvEval(self._env, construct.encode(), data.byref) != 1:
            raise CLIPSError(self._env)

        return data.value