pub fn list(&self) -> Option<&List> {
        if let Self::List(l) = self {
            Some(&l)
        } else {
            None
        }
    }
/// Retrieve &List from a value in case it is a list.
Retrieve &List from a value in case it is a list.
Retrieve &List from a value in case it is a list .
pub fn list(&self) -> Option<&List> {
        if let Self::List(l) = self {
            Some(&l)
        } else {
            None
        }
    }
pub fn list ( & self ) -> Option < & List > { if let Self :: List ( l ) = self { Some ( & l ) } else { None } }
Retrieve &List from a value in case it is a list.
Retrieve &List from a value in case it is a list .
&self
&self