message: remove unnecessary mut
diff: @@ -65,7 +65,7 @@ where
  weight_particle: f64,
  weight_swarm: f64,
  ) -> Result<Self, Error> {
  - let mut particle_swarm = ParticleSwarm {
  + let particle_swarm = ParticleSwarm {
  iter_callback: None,
  particles: vec![],
  best_position: O::Param::rand_from_range(
  