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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 _make_one_char_uppercase(string: str) -> str: """Make a single char from the string uppercase."""

        if not isinstance(string, str):
            raise TypeError('string must be a string')

        if Aux.lowercase_count(string) > 0:
            while True:
                cindex = randbelow(len(string))
                if string[cindex].islower():
                    aux = list(string)
                    aux[cindex] = aux[cindex].upper()
                    string = ''.join(aux)
                    break

        return string