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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 search_composite(self, query, source, payload=None):
        '''Shortcut search with composite source'''
        source = '+'.join(source)

        if payload is None:
            payload = dict(Sources=quote(source))
        else:
            payload['Sources'] = quote(source)

        return self.search(query, 'Composite', payload)