code: def certify_required(value, required=False):
      
      # Certify our kwargs:
      if not isinstance(required, bool):
          raise CertifierParamError(
              'required',
              required,
          )
      if value is None:
          if required:
              raise CertifierValueError(
                  message="required value is None",
              )
          return True
docs: Certify that a value is present if required.
  
      :param object value:
          The value that is to be certified.
      :param bool required:
          Is the value required?
      :raises CertifierValueError:
          Required value is `None`.