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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 varnames(self):
 """The names of all of the local variables in this code object. """

        # We must sort to preserve the order between calls.
        # The set comprehension is to drop the duplicates.
        return self._argnames + tuple(sorted({
            instr.arg
            for instr in self.instrs
            if instr.uses_varname and instr.arg not in self._argnames
        }))