def add_gid(gid, parent = nil)
      frame = Frame.new(self, gid, parent)
      add(frame)
    end
def add_gid(gid, parent = nil)
      frame = Frame.new(self, gid, parent)
      add(frame)
    end
Add a GID to the queue.

 gid    - The String GID to add to the queue.
 parent - The frame where this GID was discovered (optional).

 Returns true if a frame was added, false otherwise.