fix: usage of frappe.db.exists
diff --git a/erpnext/accounts/doctype/pos_invoice/pos_invoice.py b/erpnext/accounts/doctype/pos_invoice/pos_invoice.py
index 91c07ad..2b88fe7 100644
--- a/erpnext/accounts/doctype/pos_invoice/pos_invoice.py
+++ b/erpnext/accounts/doctype/pos_invoice/pos_invoice.py
@@ -494,7 +494,7 @@
 		}
 		pr = frappe.db.exists(args)
 		if pr:
-			return frappe.get_doc('Payment Request', pr[0][0])
+			return frappe.get_doc('Payment Request', pr)
 
 @frappe.whitelist()
 def get_stock_availability(item_code, warehouse):
diff --git a/erpnext/crm/doctype/appointment/appointment.py b/erpnext/crm/doctype/appointment/appointment.py
index 20fb987..c36faaf 100644
--- a/erpnext/crm/doctype/appointment/appointment.py
+++ b/erpnext/crm/doctype/appointment/appointment.py
@@ -229,5 +229,5 @@
 		{'doctype': 'Employee', 'user_id': user})
 	if employee_docname:
 		# frappe.db.exists returns a tuple of a tuple
-		return frappe.get_doc('Employee', employee_docname[0][0])
+		return frappe.get_doc('Employee', employee_docname)
 	return None
diff --git a/erpnext/crm/doctype/appointment/test_appointment.py b/erpnext/crm/doctype/appointment/test_appointment.py
index f4086dc..7183737 100644
--- a/erpnext/crm/doctype/appointment/test_appointment.py
+++ b/erpnext/crm/doctype/appointment/test_appointment.py
@@ -8,50 +8,53 @@
 
 
 def create_test_lead():
-    test_lead = frappe.db.exists({'doctype': 'Lead', 'email_id':'test@example.com'})
-    if test_lead:
-        return frappe.get_doc('Lead', test_lead[0][0])
-    test_lead = frappe.get_doc({
-        'doctype': 'Lead',
-        'lead_name': 'Test Lead',
-        'email_id': 'test@example.com'
-    })
-    test_lead.insert(ignore_permissions=True)
-    return test_lead
+	test_lead = frappe.db.exists({"doctype": "Lead", "email_id": "test@example.com"})
+	if test_lead:
+		return frappe.get_doc("Lead", test_lead)
+	test_lead = frappe.get_doc(
+		{"doctype": "Lead", "lead_name": "Test Lead", "email_id": "test@example.com"}
+	)
+	test_lead.insert(ignore_permissions=True)
+	return test_lead
 
 
 def create_test_appointments():
-    test_appointment = frappe.db.exists(
-        {'doctype': 'Appointment', 'scheduled_time':datetime.datetime.now(),'email':'test@example.com'})
-    if test_appointment:
-        return frappe.get_doc('Appointment', test_appointment[0][0])
-    test_appointment = frappe.get_doc({
-        'doctype': 'Appointment',
-        'email': 'test@example.com',
-        'status': 'Open',
-        'customer_name': 'Test Lead',
-        'customer_phone_number': '666',
-        'customer_skype': 'test',
-        'customer_email': 'test@example.com',
-        'scheduled_time': datetime.datetime.now()
-    })
-    test_appointment.insert()
-    return test_appointment
+	test_appointment = frappe.db.exists(
+		{
+			"doctype": "Appointment",
+			"scheduled_time": datetime.datetime.now(),
+			"email": "test@example.com",
+		}
+	)
+	if test_appointment:
+		return frappe.get_doc("Appointment", test_appointment)
+	test_appointment = frappe.get_doc(
+		{
+			"doctype": "Appointment",
+			"email": "test@example.com",
+			"status": "Open",
+			"customer_name": "Test Lead",
+			"customer_phone_number": "666",
+			"customer_skype": "test",
+			"customer_email": "test@example.com",
+			"scheduled_time": datetime.datetime.now(),
+		}
+	)
+	test_appointment.insert()
+	return test_appointment
 
 
 class TestAppointment(unittest.TestCase):
-    test_appointment = test_lead = None
+	test_appointment = test_lead = None
 
-    def setUp(self):
-        self.test_lead = create_test_lead()
-        self.test_appointment = create_test_appointments()
+	def setUp(self):
+		self.test_lead = create_test_lead()
+		self.test_appointment = create_test_appointments()
 
-    def test_calendar_event_created(self):
-        cal_event = frappe.get_doc(
-            'Event', self.test_appointment.calendar_event)
-        self.assertEqual(cal_event.starts_on,
-                         self.test_appointment.scheduled_time)
+	def test_calendar_event_created(self):
+		cal_event = frappe.get_doc("Event", self.test_appointment.calendar_event)
+		self.assertEqual(cal_event.starts_on, self.test_appointment.scheduled_time)
 
-    def test_lead_linked(self):
-        lead = frappe.get_doc('Lead', self.test_lead.name)
-        self.assertIsNotNone(lead)
+	def test_lead_linked(self):
+		lead = frappe.get_doc("Lead", self.test_lead.name)
+		self.assertIsNotNone(lead)
diff --git a/erpnext/hr/doctype/leave_application/test_leave_application.py b/erpnext/hr/doctype/leave_application/test_leave_application.py
index 7d32fd8..e01bdf6 100644
--- a/erpnext/hr/doctype/leave_application/test_leave_application.py
+++ b/erpnext/hr/doctype/leave_application/test_leave_application.py
@@ -936,7 +936,7 @@
 		"company": "_Test Company"
 	})
 	if leave_period_name:
-		return frappe.get_doc("Leave Period", leave_period_name[0][0])
+		return frappe.get_doc("Leave Period", leave_period_name)
 	else:
 		return frappe.get_doc(dict(
 				name = 'Test Leave Period',