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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_one(self, key):
 """ method finds single record base on the given primary key and returns it to the caller"""

        query = build_db_query(self.primary_key, key)
        collection = self.ds.connection(self.collection_name)

        document = collection.find_one(query)
        if document is None:
            raise LookupError('{0} with key {1} was not found'.format(self.model_klass.__name__, query))
        return self.model_klass.from_json(document)