Api params data format

From external application i am getting data through erpnext API.
We are getting data from this code frappe.local.form_dict and data structure is:

{'{"data":{"category":"baldai","brand_name":"NORE","brand":"mink\\u0161tas kampas Livio","model":"Universalus mink\\u0161tas kampas Livio"}}': u''}

Python saying it’s dictionary. But I can’t access this data and system showing error.

Note extrenal api using FrappeClient-PHP