code: function Template(style, fields, opts) {
    // throw early if style is incorrect
    if (passFields.STYLES.indexOf(style) === -1) {
      throw new Error('Incorrect passbook style ' + style)
    }
  
    this.style  = style
    this.opts   = opts   || {}
    this.fields = fields || {}
  
    // Set formatVersion by default
    this.fields.formatVersion = 1
  }
docs: Create a passbook template.
  A Template acts as a pass without having all its fields set.
  
  Internally, on createPass it merely passes its fields and the extra ones
  provided as an argument to a new Pass object
  
  @param {String} style  Pass style of the pass
  @param {Object} fields Fields of the pass
  @param {Object} opts   Extra options