keras/src/ops/numpy.py/isnan
def isnan(x):
    """Test element-wise for NaN and return result as a boolean tensor.

    Args:
        x: Input tensor.

    Returns:
        Output boolean tensor.
    """
    if any_symbolic_tensors((x,)):
        return Isnan().symbolic_call(x)
    return backend.numpy.isnan(x)