code: def varnames(self):
          
          # 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
          }))
docs: The names of all of the local variables in this code object.