code: function _getParentKeyName(ctx) {
          var parentKeyName, braceParity = 1, hasColon;
  
          // Move the context back to find the parent key.
          while (TokenUtils.moveSkippingWhitespace(TokenUtils.movePrevToken, ctx)) {
              if (ctx.token.type === null) {
                  if (ctx.token.string === "}") {
                      braceParity++;
                  } else if (ctx.token.string === "{") {
                      braceParity--;
                  }
              }
  
              if (braceParity === 0) {
                  while (TokenUtils.moveSkippingWhitespace(TokenUtils.movePrevToken, ctx)) {
                      if (ctx.token.type === null && ctx.token.string === ":") {
                          hasColon = true;
                      } else if (ctx.token.type === "string property") {
                          parentKeyName = stripQuotes(ctx.token.string);
                          break;
                      }
                  }
                  break;
              }
          }
  
          if (parentKeyName && hasColon) {
              return parentKeyName;
          }
          return null;
      }
docs: @private
  
  Returns the name of parent object
  
  @param {!{editor:!CodeMirror, pos:!{ch:number, line:number}, token:Object}} ctx
  @return {String}