code: function normalizeInput (source) {
    let result = ReducerList.parse(source)
    if (result.length === 1) {
      // do not create a ReducerList that only contains a single reducer
      result = result[0]
    }
  
    return result
  }
docs: this is here because ReducerLists can be arrays or | separated strings
  @param {*} source
  @returns {Array<reducer>|reducer}