pub fn twin(&self) -> Result<EdgeIndex, BvError> {
        self.twin_.ok_or_else(|| {
            BvError::ValueError(
                "Edge didn't have any valid twin edge associated to it.".to_string(),
            )
        })
    }
/// Returns the twin edge or an error
Returns the twin edge or an error
Returns the twin edge or an error
pub fn twin(&self) -> Result<EdgeIndex, BvError> {
        self.twin_.ok_or_else(|| {
            BvError::ValueError(
                "Edge didn't have any valid twin edge associated to it.".to_string(),
            )
        })
    }
pub fn twin ( & self ) -> Result < EdgeIndex , BvError > { self . twin_ . ok_or_else ( | | { BvError :: ValueError ( " " . to_string ( ) , ) } ) }
Returns the twin edge or an error
Returns the twin edge or an error
&self