Function extern_spec_T_A_VecDeque_T_A_is_empty 

pub fn extern_spec_T_A_VecDeque_T_A_is_empty<T, A: Allocator>(
    self_: &VecDeque<T, A>,
) -> bool

extern spec for VecDeque<T, A>::is_empty

This is not a real function: its only use is for documentation.

terminates

ghost

ensures

result == (self@.len() == 0)