keras/src/trainers/data_adapters/array_slicing.py/Sliceable/__getitem__
class Sliceable:    def __getitem__(self, indices):
        """Select elements in the 0th dimension.

        Args:
            indices: the indices to select. Only needs to support one dimension,
                the 0th dimension. Should support a `slice` or a list, tuple,
                `np.array` or 1D tensor.
        Returns: A slice of `self.array`.
        """
        return self.array[indices]