fn best_chain(&self) -> Option<&Chain> {
        self.chain_set
            .iter()
            .next_back()
            .map(|box_chain| box_chain.deref())
    }
/// Return the non-finalized portion of the current best chain
Return the non-finalized portion of the current best chain
Return the non - finalized portion of the current best chain
fn best_chain(&self) -> Option<&Chain> {
        self.chain_set
            .iter()
            .next_back()
            .map(|box_chain| box_chain.deref())
    }
fn best_chain ( & self ) -> Option < & Chain > { self . chain_set . iter ( ) . next_back ( ) . map ( | box_chain | box_chain . deref ( ) ) }
Return the non-finalized portion of the current best chain
Return the non - finalized portion of the current best chain
&self