def _is_likey_optimizer(op):
    """Return True if op is likely an optimizer.

    All operations are considered likely except those known to NOT be
    optimizers. These are '+' (the general batch op) and 'random'.

    Ideally the operation would indicate if it is an optimizer but
    Guild doesn't support an interface for this.
    """
    return op.opref.op_name not in ("+", "random")