code: function( commandName, commandDefinition ) {
  			commandDefinition.name = commandName.toLowerCase();
  			var cmd = new CKEDITOR.command( this, commandDefinition );
  
  			// Update command when mode is set.
  			// This guarantees that commands added before first editor#mode
  			// aren't immediately updated, but waits for editor#mode and that
  			// commands added later are immediately refreshed, even when added
  			// before instanceReady. #10103, #10249
  			if ( this.mode )
  				updateCommand( this, cmd );
  
  			return this.commands[ commandName ] = cmd;
  		}
docs: Adds a command definition to the editor instance. Commands added with
  this function can be executed later with the <code>{@link #execCommand}</code> method.
  
  editorInstance.addCommand( 'sample', {
  exec: function( editor ) {
  alert( 'Executing a command for the editor name "' + editor.name + '"!' );
  }
  } );
  
  @param {String} commandName The indentifier name of the command.
  @param {CKEDITOR.commandDefinition} commandDefinition The command definition.