code: function _is_same_ann(a1, a2){
      	var ret = false;
      	if( a1.key() === a2.key() &&
      	    a1.value() === a2.value() &&
      	    a1.value_type() === a2.value_type() ){
      	    ret = true;
      	}
      	return ret;
      }
docs: Function to check if two annotations are the same.