input.py 文件源码

def get_collection_iterator(self, context: Context) -> Iterator[Any]:
        collection = self._accessor.perform_access(context)
        if isinstance(collection, collections.abc.Set):  # type: ignore (mypy does not know about collections.abc)
            return iter(collection)
        elif isinstance(collection, collections.abc.Sequence):  # type: ignore (mypy does not know about collections.abc)
            return enumerate(collection)  # yields (index, element) tuples
        elif isinstance(collection, collections.abc.Mapping):  # type: ignore (mypy does not know about collections.abc)
            return iter(collection.items())  # yields (key, element) tuples
        else:
            raise ValueError(
                'During iteration {0!r}: '
                'collection object of type {1!r} could not be identified as Set, Sequence or Dictionary. '
                'It should inherit from collections.abc.Set, collections.abc.Sequence, or collections.abc.Mapping.'
                .format(self, type(collection)))