input: Write a python function to calculate the number of hours between two given times.
  assert hours_difference("1:00pm", "4:45pm") == 3.75
  assert hours_difference("2:30am", "6:30am") == 4.0
  assert hours_difference("11:00pm", "2:00am") == 3.0
output: def hours_difference(start, end):
      from datetime import datetime
  
      def convert_to_24hr(time_str):
          return datetime.strptime(time_str, "%I:%M%p").time()
  
      start_time = convert_to_24hr(start)
      end_time = convert_to_24hr(end)
  
      start_datetime = datetime.combine(datetime.today(), start_time)
      end_datetime = datetime.combine(datetime.today(), end_time)
      
      if end_datetime < start_datetime:
          end_datetime += timedelta(days=1)
  
      difference = end_datetime - start_datetime
      return difference.total_seconds() / 3600