code: def _validate_generic_parameters(self, args):
          
          utc_now = self.get_utc_time()
  
          if getattr(self, "actions", None) is not None:
              # Check the deprecated 'actions' attribute
              if not args["action"] in self.actions:
                  raise APIError(400, "InvalidAction", "The action %s is not "
                                 "valid for this web service." % args["action"])
          else:
              self.registry.check(args["action"], args["version"])
  
          if not args["signature_version"] in self.signature_versions:
              raise APIError(403, "InvalidSignature", "SignatureVersion '%s' "
                             "not supported" % args["signature_version"])
  
          if args["expires"] and args["timestamp"]:
              raise APIError(400, "InvalidParameterCombination",
                             "The parameter Timestamp cannot be used with "
                             "the parameter Expires")
          if args["expires"] and args["expires"] < utc_now:
              raise APIError(400,
                             "RequestExpired",
                             "Request has expired. Expires date is %s" % (
                                  args["expires"].strftime(self.time_format)))
          if (args["timestamp"]
              and args["timestamp"] + timedelta(minutes=15) < utc_now):
              raise APIError(400,
                             "RequestExpired",
                             "Request has expired. Timestamp date is %s" % (
                                 args["timestamp"].strftime(self.time_format)))
docs: Validate the generic request parameters.
  
          @param args: Parsed schema arguments.
          @raises APIError: In the following cases:
              - Action is not included in C{self.actions}
              - SignatureVersion is not included in C{self.signature_versions}
              - Expires and Timestamp are present
              - Expires is before the current time
              - Timestamp is older than 15 minutes.