fn boundary(&self) -> Boundary {
        Boundary {
            simplex: &self,
            index: 0,
            _phantom: PhantomData,
        }
    }
/// Returns an iteratro that produces the faces of the boundary of `self`.
Returns an iteratro that produces the faces of the boundary of `self`.
Returns an iteratro that produces the faces of the boundary of ` self ` .
fn boundary(&self) -> Boundary {
        Boundary {
            simplex: &self,
            index: 0,
            _phantom: PhantomData,
        }
    }
fn boundary ( & self ) -> Boundary { Boundary { simplex : & self , index : 0 , _phantom : PhantomData , } }
Returns an iteratro that produces the faces of the boundary of `self`.
Returns an iteratro that produces the faces of the boundary of ` self ` .
&self
&self