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 );
  
  			// If default configuration (will be checked inside #allow()),
  			// then add allowed content rules.
  			this.allow( feature.allowedContent, feature.name );
  
  			this.addTransformations( feature.contentTransformations );
  			this.addContentForms( feature.contentForms );
  
  			// If custom configuration or any DACRs, then check if required content is allowed.
  			if ( feature.requiredContent && ( this.customConfig || this.disallowedContent.length ) )
  				return this.check( feature.requiredContent );
  
  			return true;
  		}
docs: Checks whether a feature can be enabled for the HTML restrictions in place
  for the current CKEditor instance, based on the HTML code the feature might
  generate and the minimal HTML code the feature needs to be able to generate.
  
  // TODO example
  
  @param {CKEDITOR.feature} feature
  @returns {Boolean} Whether this feature can be enabled.