code: def value_validate(self, value):
          
          if not isinstance(value, str):
              raise tldap.exceptions.ValidationError("Invalid sid")
  
          array = value.split("-")
          length = len(array) - 3
  
          if length < 1:
              raise tldap.exceptions.ValidationError("Invalid sid")
  
          if array.pop(0) != "S":
              raise tldap.exceptions.ValidationError("Invalid sid")
  
          try:
              [int(i) for i in array]
          except TypeError:
              raise tldap.exceptions.ValidationError("Invalid sid")
docs: Converts the input single value into the expected Python data type,
          raising django.core.exceptions.ValidationError if the data can't be
          converted.  Returns the converted value. Subclasses should override
          this.