chore: remove all six compat code
diff --git a/erpnext/stock/get_item_details.py b/erpnext/stock/get_item_details.py
index 6de04c4..438d3eb 100644
--- a/erpnext/stock/get_item_details.py
+++ b/erpnext/stock/get_item_details.py
@@ -8,7 +8,6 @@
 from frappe import _, throw
 from frappe.model.meta import get_field_precision
 from frappe.utils import add_days, add_months, cint, cstr, flt, getdate
-from six import iteritems, string_types
 
 from erpnext import get_company_currency
 from erpnext.accounts.doctype.pricing_rule.pricing_rule import (
@@ -58,7 +57,7 @@
 
 	out = get_basic_details(args, item, overwrite_warehouse)
 
-	if isinstance(doc, string_types):
+	if isinstance(doc, str):
 		doc = json.loads(doc)
 
 	if doc and doc.get('doctype') == 'Purchase Invoice':
@@ -97,7 +96,7 @@
 		out.update(bin_details)
 
 	# update args with out, if key or value not exists
-	for key, value in iteritems(out):
+	for key, value in out.items():
 		if args.get(key) is None:
 			args[key] = value
 
@@ -162,7 +161,7 @@
 
 
 def process_args(args):
-	if isinstance(args, string_types):
+	if isinstance(args, str):
 		args = json.loads(args)
 
 	args = frappe._dict(args)
@@ -179,7 +178,7 @@
 	return args
 
 def process_string_args(args):
-	if isinstance(args, string_types):
+	if isinstance(args, str):
 		args = json.loads(args)
 	return args
 
@@ -1173,7 +1172,7 @@
 @frappe.whitelist()
 def get_serial_no(args, serial_nos=None, sales_order=None):
 	serial_no = None
-	if isinstance(args, string_types):
+	if isinstance(args, str):
 		args = json.loads(args)
 		args = frappe._dict(args)
 	if args.get('doctype') == 'Sales Invoice' and not args.get('update_stock'):
@@ -1202,7 +1201,7 @@
 
 @frappe.whitelist()
 def get_blanket_order_details(args):
-	if isinstance(args, string_types):
+	if isinstance(args, str):
 		args = frappe._dict(json.loads(args))
 
 	blanket_order_details = None