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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 all_solidity_variables_used_as_args(self):
 """ Return the Soldiity variables directly used in a call Use of the IR to filter index access Used to catch check(msg.sender) """

        if self._all_solidity_variables_used_as_args is None:
            self._all_solidity_variables_used_as_args = self._explore_functions(
                lambda x: self._explore_func_nodes(x, self._solidity_variable_in_internal_calls))
        return self._all_solidity_variables_used_as_args