keras/src/ops/numpy.py/Meshgrid/__init__
class Meshgrid:    def __init__(self, indexing="xy"):
        super().__init__()
        if indexing not in ("xy", "ij"):
            raise ValueError(
                "Valid values for `indexing` are 'xy' and 'ij', "
                "but received {index}."
            )
        self.indexing = indexing