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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_mapping(self, superset, subset):
 """ Calculate the mapping from superset to subset. Args: superset (Structure):
 Structure containing at least the sites in subset (within the structure matching tolerance) subset (Structure):
 Structure containing some of the sites in superset (within the structure matching tolerance) Returns: numpy array such that superset.sites[mapping] is within matching tolerance of subset.sites or None if no such mapping is possible """

        if self._supercell:
            raise ValueError("cannot compute mapping to supercell")
        if self._primitive_cell:
            raise ValueError("cannot compute mapping with primitive cell "
                             "option")
        if len(subset) > len(superset):
            raise ValueError("subset is larger than superset")

        superset, subset, _, _ = self._preprocess(superset, subset, True)
        match = self._strict_match(superset, subset, 1, break_on_match=False)

        if match is None or match[0] > self.stol:
            return None

        return match[4]