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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 replace(self, replacements):
 """ Replace variables with other variables. :param dict replacements: A dict of variable replacements. :return: self """


        for old_var, new_var in replacements.items():
            old_var_id = id(old_var)
            if old_var_id in self._object_mapping:
                # FIXME: we need to check if old_var still exists in the storage
                old_so = self._object_mapping[old_var_id]  # type: StoredObject
                self._store(old_so.start, new_var, old_so.size, overwrite=True)

        return self