Function igraph_get_eid 

pub unsafe extern "C" fn igraph_get_eid(
    graph: *const igraph_t,
    eid: *mut igraph_int_t,
    from: igraph_int_t,
    to: igraph_int_t,
    directed: igraph_bool_t,
    error: igraph_bool_t,
) -> igraph_error_t