Macro generalized_quad 

macro_rules! generalized_quad {
    {
        @from ($($acc:tt)*) << ( $($body:tt)* ) >> $($rest:tt)*
    } => { ... };
    {
        @from ($($acc:tt)*) $id:ident $($rest:tt)*
    } => { ... };
    {
        @from ($($acc:tt)*) < $iri:literal > $($rest:tt)*
    } => { ... };
    {
        @from ($($acc:tt)*) _ : $id:literal $($rest:tt)*
    } => { ... };
    {
        @from ($($acc:tt)*) $value:literal ^^ $ty:literal $($rest:tt)*
    } => { ... };
    {
        @from ($($acc:tt)*) $value:literal @ $lang:literal / $dir:literal $($rest:tt)*
    } => { ... };
    {
        @from ($($acc:tt)*) $value:literal @ $lang:literal $($rest:tt)*
    } => { ... };
    {
        @from ($($acc:tt)*) $value:literal $($rest:tt)*
    } => { ... };
    {
        @from ($s:expr, $p:expr, $o:expr,)
    } => { ... };
    {
        @from ($s:expr, $p:expr, $o:expr, $g:expr,)
    } => { ... };
    {
        @from ($($acc:tt)*) $t:tt $($rest:tt)*
    } => { ... };
    {
        $($t:tt)*
    } => { ... };
}

Creates a generalized RDF quad (GeneralizedQuad<LocalTerm>).