chore: remove all six compat code

erpnext/accounts/utils.py

@@ -9,7 +9,6 @@ import frappe.defaults
 from frappe import _, throw
 from frappe.model.meta import get_field_precision
 from frappe.utils import cint, cstr, flt, formatdate, get_number_format_info, getdate, now, nowdate
-from six import string_types
 
 import erpnext
 
@@ -795,7 +794,7 @@ def get_children(doctype, parent, company, is_root=False):
 @frappe.whitelist()
 def get_account_balances(accounts, company):
 
-	if isinstance(accounts, string_types):
+	if isinstance(accounts, str):
 		accounts = loads(accounts)
 
 	if not accounts: