code: def parse_date(s):
      
      if isinstance(s, (datetime.datetime, datetime.date)):
          return s
      try:
          from dateutil.parser import parse
      except ImportError:
          parse = lambda d: datetime.datetime.strptime(d, "%Y-%m-%d")
      return parse(s)
docs: Parse a date using dateutil.parser.parse if available,
      falling back to datetime.datetime.strptime if not