docs: function (field) {
              var schemaDefinition = this.schema[field];
              if (!schemaDefinition) {
                  throw "Couldn't find '" + field + "' in schema";
              }
              var collection = this.get(field);
              if (!collection) {
                  var context = this.getContextForChild(schemaDefinition.type);
                  if (context) {
                      collection = context.createCollection(schemaDefinition.type, null);
                      collection.$parent = this;
                      this.set(field, collection);
                  } else {
                      throw "Couldn't determine context for " + field;
                  }
              }
              return collection;
  
  
          }