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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 request_headers(self, request):
 """ Generate standard request headers """

        headers = {}

        allow_origin = self.allow_origin(request)
        if allow_origin:
            headers = dict_filter({
                'Access-Control-Allow-Origin': allow_origin,
                'Access-Control-Allow-Credentials': {True: 'true', False: 'false'}.get(self.allow_credentials),
                'Access-Control-Expose-Headers': ', '.join(self.expose_headers) if self.expose_headers else None,
            })

        return headers