code: function assert (assert, code, customMessage, original, data) {
      return immutableError.assert(assert, this, code, customMessage, original, data)
  }
docs: @function assert
  
  assert that value is true - throw error if false
  
  @param {boolean} assert
  @param {number} code
  @param {string} customMessage
  @param {Error} original
  @param {object} data
  
  @throws {Error}