code: def add_schedule_expression_arg(parser):
      """Add the schedule expression argument to a parser"""
  
      def _validator(val):
          """Validate the schedule expression rate value for acceptable input"""
          rate_match = AWS_RATE_RE.match(val)
          if rate_match:
              return val
  
          if val.startswith("rate("):
              err = "Invalid rate expression '{}'. For help see {}".format(
                  val, "{}#RateExpressions".format(AWS_RATE_HELPER)
              )
              raise parser.error(err)
  
          raise parser.error(
              "Invalid expression '{}'. For help "
              "see {}".format(val, AWS_RATE_HELPER)
          )
  
      schedule_help = (
          "The interval, defined using a 'rate' expression, at which this function should "
          "execute. Examples of acceptable input are: 'rate(1 hour)', 'rate(2 days)', and "
          "'rate(20 minutes)'. For more information, see: {}"
      ).format(AWS_RATE_HELPER)
  
      parser.add_argument(
          "-s",
          "--schedule-expression",
          required=True,
          help=schedule_help,
          type=_validator,
      )
  
imports: from abc import abstractmethod
  from argparse import _AppendAction, Action, ArgumentTypeError, RawDescriptionHelpFormatter
  import os
  import textwrap
  from streamalert.apps.config import AWS_RATE_RE, AWS_RATE_HELPER
label_desc: Use image node_id 4 for calling a global function with example usage: add_schedule_expression_arg(parser) and returns: val