How to override method which is not class method or whitelisted method?

Hello Everyone,
How to override method that is neither whitelisted nor class:

def send_event_digest():
	today = nowdate()

	# select only those users that have event reminder email notifications enabled
	users = [
		for user in get_enabled_system_users()
		if is_email_notifications_enabled_for_type(, "Event Reminders")

	for user in users:
		events = get_events(today, today,, for_reminder=True)
		if events:
			frappe.set_user_lang(, user.language)

			for e in events:
				e.starts_on = format_datetime(e.starts_on, "hh:mm a")
				if e.all_day:
					e.starts_on = "All Day"

				subject=frappe._("Upcoming Events for Today"),
					"events": events,
				header=[frappe._("Events in Today's Calendar"), "blue"],

I want to update the message

Hi @Anisha_Jain
Please Read This Document. I hope It will help you
Thank You!