This symbol is a type alias.
Source:
NestedTensor = Union[
tensorflow.python.framework.tensor.Tensor,
tensorflow.python.framework.sparse_tensor.SparseTensor,
tensorflow.python.ops.ragged.ragged_tensor.RaggedTensor,
tensorflow.python.framework.ops.EagerTensor,
Iterable[ForwardRef('NestedTensor')],
Mapping[str, ForwardRef('NestedTensor')]
]