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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 _get_codepage_char_map(self, encoding):
 """ Get codepage character map Process an encoding and return a map of UTF-characters to code points in this encoding. This is generated once only, and returned from a cache. :param encoding: The name of the encoding. """

        # Skip things that were loaded previously
        if encoding in self.available_characters:
            return self.available_characters[encoding]
        codepage_char_list = self._get_codepage_char_list(encoding)
        codepage_char_map = dict((utf8, i + 128) for (i, utf8) in enumerate(codepage_char_list))
        self.available_characters[encoding] = codepage_char_map
        return codepage_char_map