style: use double quotes
diff --git a/erpnext/accounts/doctype/dunning/dunning.py b/erpnext/accounts/doctype/dunning/dunning.py
index 56d49df..79de03c 100644
--- a/erpnext/accounts/doctype/dunning/dunning.py
+++ b/erpnext/accounts/doctype/dunning/dunning.py
@@ -21,7 +21,7 @@
 		self.validate_totals()
 
 		if not self.income_account:
-			self.income_account = frappe.get_cached_value("Company", self.company, "default_income_account")
+			self.income_account = frappe.db.get_value("Company", self.company, "default_income_account")
 
 	def validate_overdue_payments(self):
 		for row in self.overdue_payments:
@@ -36,13 +36,13 @@
 		grand_total = flt(total_outstanding) + flt(dunning_amount)
 
 		if self.total_outstanding != total_outstanding:
-			self.total_outstanding = flt(total_outstanding, self.precision('total_outstanding'))
+			self.total_outstanding = flt(total_outstanding, self.precision("total_outstanding"))
 		if self.total_interest != total_interest:
-			self.total_interest = flt(total_interest, self.precision('total_interest'))
+			self.total_interest = flt(total_interest, self.precision("total_interest"))
 		if self.dunning_amount != dunning_amount:
-			self.dunning_amount = flt(dunning_amount, self.precision('dunning_amount'))
+			self.dunning_amount = flt(dunning_amount, self.precision("dunning_amount"))
 		if self.grand_total != grand_total:
-			self.grand_total = flt(grand_total, self.precision('grand_total'))
+			self.grand_total = flt(grand_total, self.precision("grand_total"))
 
 	def on_submit(self):
 		self.make_gl_entries()
diff --git a/erpnext/accounts/doctype/sales_invoice/sales_invoice.py b/erpnext/accounts/doctype/sales_invoice/sales_invoice.py
index f240fe9..05f8638 100644
--- a/erpnext/accounts/doctype/sales_invoice/sales_invoice.py
+++ b/erpnext/accounts/doctype/sales_invoice/sales_invoice.py
@@ -2516,7 +2516,7 @@
 	def postprocess_dunning(source, target):
 		from erpnext.accounts.doctype.dunning.dunning import get_dunning_letter_text
 
-		dunning_type = frappe.db.exists('Dunning Type', {'is_default': 1})
+		dunning_type = frappe.db.exists("Dunning Type", {"is_default": 1})
 		if dunning_type:
 			dunning_type = frappe.get_doc("Dunning Type", dunning_type)
 			target.dunning_type = dunning_type.name
@@ -2529,9 +2529,9 @@
 			)
 
 			if letter_text:
-				target.body_text = letter_text.get('body_text')
-				target.closing_text = letter_text.get('closing_text')
-				target.language = letter_text.get('language')
+				target.body_text = letter_text.get("body_text")
+				target.closing_text = letter_text.get("closing_text")
+				target.language = letter_text.get("language")
 
 		target.validate()