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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 get_existing_keyword(self, keyword):
 """Obtain an existing keyword's value. :param keyword: A keyword from keywords. :type keyword: str :returns: The value of the keyword. :rtype: str, QUrl """

        if self.existing_keywords is None:
            return {}
        if keyword is not None:
            return self.existing_keywords.get(keyword, {})
        else:
            return {}