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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(cls, ns, key):
 """Fetch an item by namespace and key Args: ns (str):
 Namespace prefix key (str):
 Item key Returns: :obj:`Configitem`: Returns config item object if found, else `None` """

        return getattr(db, cls.__name__).find_one(
            ConfigItem.namespace_prefix == ns,
            ConfigItem.key == key
        )