code: @SuppressWarnings("WeakerAccess") // Public exposed for usage outside SDK
    public void removeMilestone(@Nullable Milestone milestone) {
      if (milestone == null) {
        milestones.clear();
        return;
      } else if (!milestones.contains(milestone)) {
        Timber.w("Milestone attempting to remove does not exist in stack.");
        return;
      }
      milestones.remove(milestone);
    }
docs: Remove a specific milestone by passing in the instance of it. Removal of all the milestones can
  be achieved by passing in null rather than a specific milestone.
  
  @param milestone a milestone you'd like to have removed or null if you'd like to remove all
  milestones
  @since 0.4.0