Create a new dataset from the contents of a backends.*DataStore
        object

def load_store(cls, store, decoder=None):
        """Create a new dataset from the contents of a backends.*DataStore
        object
        """
        variables, attributes = store.load()
        if decoder:
            variables, attributes = decoder(variables, attributes)
        obj = cls(variables, attrs=attributes)
        obj._file_obj = store
        return obj