How to filter basing on parent_permalink in getDiscussionsByCreated method

[swapnachippagi]

in this url link to steemit (discussion_query) , i have given parent_permalink but geting unknown key error

var query = {
    tag: 'dmania',
    limit: 10,
	 
	parent_author :'dmania',
  parent_permlink:'dmania'
};
steem.api.getDiscussionsByCreated(query, function(err, result) {
   console.log(err, result);
 
});

how can i get only from the parent_permalink ? Thanks

[yashwanth2804]

Is there a way to solve this , what about parent_author to be a null value getting

Error: unknown key:unknown key: 
    at new e (steem.min.js:4)
    at steem.min.js:4 undefined