old_contents: """Utility functions and classes for track backends"""
  
  import json
  from datetime import datetime, date
  
  from pytz import UTC
  
  
  class DateTimeJSONEncoder(json.JSONEncoder):
      """JSON encoder aware of datetime.datetime and datetime.date objects"""
  
      def default(self, obj):  # pylint: disable=method-hidden
          """
          Serialize datetime and date objects of iso format.
  
          datatime objects are converted to UTC.
          """
  
          if isinstance(obj, datetime):
              if obj.tzinfo is None:
                  # Localize to UTC naive datetime objects
                  obj = UTC.localize(obj)
              else:
                  # Convert to UTC datetime objects from other timezones
                  obj = obj.astimezone(UTC)
              return obj.isoformat()
          elif isinstance(obj, date):
              return obj.isoformat()
  
          return super(DateTimeJSONEncoder, self).default(obj)
  
new_contents: """Utility functions and classes for track backends"""
  
  import json
  from datetime import datetime, date
  
  from pytz import UTC
  
  
  class DateTimeJSONEncoder(json.JSONEncoder):
      """JSON encoder aware of datetime.datetime and datetime.date objects"""
  
      def default(self, obj):  # pylint: disable=method-hidden
          """
          Serialize datetime and date objects of iso format.
  
          datetime objects are converted to UTC.
          """
  
          if isinstance(obj, datetime):
              if obj.tzinfo is None:
                  # Localize to UTC naive datetime objects
                  obj = UTC.localize(obj)
              else:
                  # Convert to UTC datetime objects from other timezones
                  obj = obj.astimezone(UTC)
              return obj.isoformat()
          elif isinstance(obj, date):
              return obj.isoformat()
  
          return super(DateTimeJSONEncoder, self).default(obj)
  
subject: Fix the misspell in docstring