Check the method is well constructed.

def Validate(self):
    """Check the method is well constructed."""
    if not self.check_id:
      raise DefinitionError("Check has missing check_id value")
    cls_name = self.check_id
    if not self.method:
      raise DefinitionError("Check %s has no methods" % cls_name)
    ValidateMultiple(self.method,
                     "Check %s has invalid method definitions" % cls_name)