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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 convert_case(self, value, case):
 """Convert case."""


        if self.is_bytes:
            cased = []
            for c in value:
                if c in _ASCII_LETTERS:
                    cased.append(c.lower() if case == _LOWER else c.upper())
                else:
                    cased.append(c)
            return "".join(cased)
        else:
            return value.lower() if case == _LOWER else value.upper()