code: def is_email(address, check_dns=False, diagnose=False):
      
  
      threshold = BaseDiagnosis.CATEGORIES["THRESHOLD"]
      d = ParserValidator().is_email(address, True)
      if check_dns is True and d < BaseDiagnosis.CATEGORIES["DNSWARN"]:
          threshold = BaseDiagnosis.CATEGORIES["VALID"]
          d = max(d, DNSValidator().is_valid(address.split("@")[1], True))
  
      return d if diagnose else d < threshold
docs: Validate an email address.
  
      Keyword arguments:
      address   --- the email address as a string
      check_dns --- flag for whether to check the DNS status of the domain
      diagnose  --- flag for whether to return True/False or a Diagnosis