code: def keep_max_priority_effects(effects):
      
      priority_values = map(effect_priority, effects)
      max_priority = max(priority_values)
      return [e for (e, p) in zip(effects, priority_values) if p == max_priority]
docs: Given a list of effects, only keep the ones with the maximum priority
      effect type.
  
      Parameters
      ----------
      effects : list of MutationEffect subclasses
  
      Returns list of same length or shorter