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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 inject_url_defaults(self, endpoint: str, values: dict) -> None: """Injects default URL values into the passed values dict. This is used to assist when building urls, see :func:`~quart.helpers.url_for`. """

        functions = self.url_value_preprocessors[None]
        if '.' in endpoint:
            blueprint = endpoint.rsplit('.', 1)[0]
            functions = chain(functions, self.url_value_preprocessors[blueprint])  # type: ignore

        for function in functions:
            function(endpoint, values)