code: function clean(attribute) {
      expect(arguments).to.have.length.below(
        2,
        'Invalid arguments length when cleaning an Entity attribute (it has ' +
        'to be passed less than 2 arguments)'
      );
  
      var attributes = this.Entity.attributes;
  
      if (attribute) {
        expect(attribute).to.be.a(
          'string',
          'Invalid argument "attribute" when cleaning an Entity attribute (it ' +
          'has to be a string)'
        );
  
        expect(attributes).to.have.ownProperty(
          attribute,
          'Invalid argument "attribute" when cleaning an Entity attribute ' +
          '(this attribute does not exist in the Entity)'
        );
  
        var newAttributes = {};
        newAttributes[attribute] = attributes[attribute];
        attributes = newAttributes;
      }
  
      for (var attributeName in attributes) {
        _attributeStorageValues[attributeName] = this[attributeName];
        _attributeIsSet[attributeName] = false;
      }
    }
docs: Cleans an Entity attribute.
  @name module:back4app-entity/models.Entity#clean
  @function
  @param {?string} [attribute] The name of the attribute to be cleaned. If no
  attribute is passed, all attributes will be cleaned.
  @example
  myEntity.clean('myAttribute'); // Cleans attribute "myAttribute" of
  // Entity "myEntity"
  @example
  myEntity.clean();              // Cleans all attributes of "myEntity"