perf: improve mapping function speed
diff --git a/erpnext/accounts/doctype/payment_request/payment_request.py b/erpnext/accounts/doctype/payment_request/payment_request.py
index 64c4124..9b0ef42 100644
--- a/erpnext/accounts/doctype/payment_request/payment_request.py
+++ b/erpnext/accounts/doctype/payment_request/payment_request.py
@@ -14,7 +14,6 @@
 from frappe.utils.background_jobs import enqueue
 from erpnext.erpnext_integrations.stripe_integration import create_stripe_subscription
 from erpnext.accounts.doctype.subscription_plan.subscription_plan import get_plan_rate
-from frappe.model.mapper import get_mapped_doc
 
 class PaymentRequest(Document):
 	def validate(self):
@@ -426,6 +425,7 @@
 
 @frappe.whitelist()
 def make_payment_order(source_name, target_doc=None):
+	from frappe.model.mapper import get_mapped_doc
 	def set_missing_values(source, target):
 		target.append('references', {
 			'reference_doctype': source.reference_doctype,
@@ -444,4 +444,4 @@
 		}
 	}, target_doc, set_missing_values)
 
-	return doclist
+	return doclist
\ No newline at end of file