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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 identifier(self):
 """ A unique identifier for the path. Returns --------- identifier: (5,) float, unique identifier """

        if len(self.polygons_full) != 1:
            raise TypeError('Identifier only valid for single body')
        return polygons.polygon_hash(self.polygons_full[0])