keras/src/layers/preprocessing/index_lookup.py/IndexLookup/compute_output_spec
class IndexLookup:    def compute_output_spec(self, inputs):
        if self.output_mode == "int":
            output_dtype = "int64"
        else:
            output_dtype = backend.floatx()
        output_shape = self.compute_output_shape(inputs.shape)
        return backend.KerasTensor(output_shape, dtype=output_dtype)