pub fn pop_front(&mut self) -> Option<K> {
        match self.0.pop_front() {
            Some((k, _)) => Some(k),
            None => None
        }
    }
/// returns the first element from the set
returns the first element from the set
returns the first element from the set
pub fn pop_front(&mut self) -> Option<K> {
        match self.0.pop_front() {
            Some((k, _)) => Some(k),
            None => None
        }
    }
pub fn pop_front ( & mut self ) -> Option < K > { match self . 0 . pop_front ( ) { Some ( ( k , _ ) ) => Some ( k ) , None => None } }
returns the first element from the set
returns the first element from the set
&mut self
&mut self