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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 dst_to_src(self, dst_file):
 """Return the src URI from the dst filepath. This does not rely on the destination filepath actually existing on the local filesystem, just on pattern matching. Return source URI on success, None on failure. """

        m = re.match(self.dst_path + "/(.*)$", dst_file)
        if (m is None):
            return(None)
        rel_path = m.group(1)
        return(self.src_uri + '/' + rel_path)