code: function( feature ) {
  			if ( this.disabled )
  				return true;
  
  			if ( !feature )
  				return true;
  
  			// Some features may want to register other features.
  			// E.g. a button may return a command bound to it.
  			if ( feature.toFeature )
  				feature = feature.toFeature( this.editor );
  
  			return !feature.requiredContent || this.check( feature.requiredContent );
  		}
docs: Checks whether a {@link CKEDITOR.feature} can be enabled. Unlike {@link #addFeature},
  this method always checks the feature, even when the default configuration
  for {@link CKEDITOR.config#allowedContent} is used.
  
  // TODO example
  
  @param {CKEDITOR.feature} feature The feature to be tested.
  @returns {Boolean} Whether this feature can be enabled.