pub fn with_key(mut self, mut indices: Vec<usize>) -> Self {
        indices.sort_unstable();
        if !self.keys.contains(&indices) {
            self.keys.push(indices);
        }
        self
    }
/// Adds a new key for the relation.
Adds a new key for the relation.
Adds a new key for the relation .
pub fn with_key(mut self, mut indices: Vec<usize>) -> Self {
        indices.sort_unstable();
        if !self.keys.contains(&indices) {
            self.keys.push(indices);
        }
        self
    }
pub fn with_key ( mut self , mut indices : Vec < usize > ) -> Self { indices . sort_unstable ( ) ; if ! self . keys . contains ( & indices ) { self . keys . push ( indices ) ; } self }
Adds a new key for the relation.
Adds a new key for the relation .
mut self
indices
Vec<usize>
mut self
indices
Vec<usize>