Returns the response header value for the given header, which may
        either be a string (not case-sensitive) or the raw byte
        value of the header ID.

        Returns the specified default value if the header is not present.

def getheader(self, header, default=None):
        '''
        Returns the response header value for the given header, which may
        either be a string (not case-sensitive) or the raw byte
        value of the header ID.

        Returns the specified default value if the header is not present.
        '''
        if isinstance(header, str):
            return self.headers.get(header.lower(), default)
        return self.__rawheaders.get(header, default)