docs: function(that) {
  		var summ = this._bugsummary;
  		var name = that.constructor.$classname || String(that);
  		console.error([
  			"Bad argument " + summ.shift(),
  			"for " + name + ":",
  			"Expected " + summ.shift() + ",",
  			"got " + summ.shift() + ":",
  			summ.shift()
  		].join(" "));
  	}