code: public boolean hasEagerSingletonBindingInSubtree() {
      if (hasEagerSingletonBinding()) {
        return true;
      }
  
      for (GinjectorBindings child : getChildren()) {
        if (child.hasEagerSingletonBindingInSubtree()) {
          return true;
        }
      }
  
      return false;
    }
docs: Returns {@code true} if any binding in this injector or in one of its
  descendants is an eager singleton binding.
  
  <p>Note: this method is Omega(n) in the height of the injector tree, and
  invoking it on every entry in the injector tree is O(n^2).  The latter cost
  could be reduced to O(n) by caching the return value.