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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 single_case(self, i, case):
 """Uppercase or lowercase the next character."""


        # Pop a previous case if we have consecutive ones.
        if self.single_stack:
            self.single_stack.pop()
        self.single_stack.append(case)
        try:
            t = next(i)
            if self.use_format and t in _CURLY_BRACKETS:
                self.handle_format(t, i)
            elif t == '\\':
                try:
                    t = next(i)
                    self.reference(t, i)
                except StopIteration:
                    self.result.append(t)
                    raise
            elif self.single_stack:
                self.result.append(self.convert_case(t, self.get_single_stack()))
        except StopIteration:
            pass