code: function ( x ) {
  
  		if ( Util.is.Error( x ) ) {
  			return this.reject( x );
  		}
  
  		// Promise Resolution Procedure: https://github.com/promises-aplus/promises-spec#the-promise-resolution-procedure
  		try {
  
  			if ( x === this ) {
  				throw new TypeError('A promise cannot be resolved with itself.');
  			}
  
  			if ( Util.is.Promise( x ) || ( x !== null && Util.is.Object( x ) && Util.is.Function( x.then ) ) ) {
  				Promise.doResolve( x.then.bind( x ), this.resolve, this.reject );
  				return this;
  			}
  
  			if ( Util.is.Function( x ) ) {
  				Promise.doResolve( x, this.resolve, this.reject );
  				return this;
  			}
  
  			this.fulfill( x );
  
  		} catch ( error ) {
  
  			return this.reject( error );
  
  		}
  
  		return this;
  	}
docs: INNER API METHODS