Macro caffe2_imports::op_single_arg

macro_rules! op_single_arg {
    ($type:ident, 
    $name:ident, 
    $variable:ident, 
    $default:ident) => { ... };
}

| OP_SINGLE_ARG provides a shorter initialization | choice for initialization of member | variables for the class constructors. | | This is a workaround for CUDA9.2 and | GCC7 |