docs: function (type, handler) {
  
              // Validate arguments
              if (typeof type !== 'string') {
                  throw new Error('Type must be a string');
              }
              if (typeof handler !== 'function') {
                  throw new Error('Handler must be a function');
              }
  
              // Check for presence of event store
              if (!this._events) {
                  this._events = {};
              }
              if (!this._events[type]) {
                  this._events[type] = [];
              }
  
              // Add handler
              this._events[type].push(handler);
  
          }