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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 content_type(self, mime_type: Optional[MimeType] = None) -> str: """Get a random HTTP content type. :return: Content type. :Example: Content-Type: application/json """

        fmt = self.__file.mime_type(type_=mime_type)
        return 'Content-Type: {}'.format(fmt)