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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 adjust_uri(self, uri, relativeto):
 """Adjust the given ``uri`` based on the given relative URI."""


        key = (uri, relativeto)
        if key in self._uri_cache:
            return self._uri_cache[key]

        if uri[0] != '/':
            if relativeto is not None:
                v = self._uri_cache[key] = posixpath.join(
                                            posixpath.dirname(relativeto), uri)
            else:
                v = self._uri_cache[key] = '/' + uri
        else:
            v = self._uri_cache[key] = uri
        return v