code: function(json){
      
      // Protect against forgetting the new keyword when calling the constructor
      if(!(this instanceof AtomFeed)){
        return new AtomFeed(json);
      }
      
      // If the given object is already an instance then just return it. DON'T copy it.
      if(AtomFeed.isInstance(json)){
        return json;
      }
      
      this.init(json);
    }
docs: The Atom data formats provide a format for web content and metadata syndication.
  The JSON data format is specific to GEDCOM X and is a translation to JSON from the XML.
  
  @see {@link https://github.com/FamilySearch/gedcomx-rs/blob/master/specifications/atom-model-specification.md#atom-json-media-type|GEDCOM X Atom JSON Spec}
  @see {@link https://tools.ietf.org/html/rfc4287#section-4.1.1|RFC 4287}
  
  @class AtomFeed
  @extends AtomCommon
  @param {Object} [json]