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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 _relativePath(self, fullPath):
 """ Return fullPath relative to Store directory. Return fullPath if fullPath is not inside directory. Return None if fullPath is outside our scope. """

        if fullPath is None:
            return None

        assert fullPath.startswith("/"), fullPath

        path = os.path.relpath(fullPath, self.userPath)

        if not path.startswith("../"):
            return path
        elif self.ignoreExtraVolumes:
            return None
        else:
            return fullPath