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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 _explain(self, tree):
 """ Set up the engine to do a dry run of a query """

        self._explaining = True
        self._call_list = []
        old_call = self.connection.call

        def fake_call(command, **kwargs):
            """ Replacement for connection.call that logs args """
            if command == "describe_table":
                return old_call(command, **kwargs)
            self._call_list.append((command, kwargs))
            raise ExplainSignal

        self.connection.call = fake_call
        try:
            ret = self._run(tree[1])
            try:
                list(ret)
            except TypeError:
                pass
        finally:
            self.connection.call = old_call
            self._explaining = False