warning: length comparison to zero
   --> src/websocket/mod.rs:204:24
    |
204 |                     if self.outgoing_keep_alive_set.len() > 0 {
    |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: using `!is_empty` is clearer and more explicit: `!self.outgoing_keep_alive_set.is_empty()`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#len_zero
    = note: `#[warn(clippy::len_zero)]` on by default