code: function addStageBlock(that, id, type, positions) {
          // Begin stage block (closes two: steps and stage).
          if (that.currentType !== BLOCK_DEFAULT) that.endBlocks(2);
          that.currentType = BLOCK_DEFAULT;
          addBlock(that, id, type, positions, BLOCK_STAGE);
      }
docs: #### addStageBlock
  
  Close last step and stage blocks and add a new stage block
  
  @param {Stager} that The stager instance
  @param {string} id Optional. The id of the stage block
  @param {string} type The type of the stage block
  @param {string|number} The allowed positions for the block
  
  @see addBlock