code: function concat(attributeDictionary, attribute) {
    expect(arguments).to.have.length(
      2,
      'Invalid arguments length when concatenating an AttributeDictionary (it ' +
      'has to be passed 2 arguments)'
    );
  
    expect(attributeDictionary).to.be.instanceof(
      AttributeDictionary,
      'Invalid argument "attributeDictionary" when concatenating an ' +
      'AttributeDictionary (it has to be an AttributeDictionary)'
    );
  
    expect(attribute).to.be.instanceof(
      Attribute,
      'Invalid argument "attribute" when concatenating an AttributeDictionary ' +
      '(it has to be an Attribute)'
    );
  
    var currentAttributes = [];
  
    for (var currentAttribute in attributeDictionary) {
      currentAttributes.push(attributeDictionary[currentAttribute]);
    }
  
    currentAttributes.push(attribute);
  
    return new AttributeDictionary(currentAttributes);
  }
docs: Concatenates an AttributeDictionary instance with an Attribute instance and
  returns a new AttributeDictionary.
  @name module:back4app-entity/models/attributes.AttributeDictionary.concat
  @function
  @param {!module:back4app-entity/models/attributes.AttributeDictionary}
  attributeDictionary The AttributeDictionary to be concatenated.
  @param {!module:back4app-entity/models/attributes.Attribute} attribute
  The Attribute to be concatenated.
  @returns {module:back4app-entity/models/attributes.AttributeDictionary} The
  new concatenated AttributeDictionary.
  @example
  var concatenatedAttributeDictionary = AttributeDictionary.concat(
  attributeDictionary,
  attribute
  );