code: function asynchChainDone(self, res) {
  			if (typeof res !== 'undefined') {
  				if (res instanceof Error) {
  					self._state.success = null;
  					self._state.error = res;
  				} else {
  					if (res && res._deep_undefined_)
  						res = undefined;
  					self._state.success = res;
  					self._state.error = null;
  				}
  			}
  			self._running = false; // asynch flag
  			if (!self._executing) // real asynch event
  				self._next();
  		}
docs: _____________________________________________________________________ PROMISED CHAIN MECANIC