code: def add_clusters_arg(parser, required=False):
      """Add ability to select 0 or more clusters to act against"""
      kwargs = {
          "choices": CLUSTERS,
          "help": (
              "One or more clusters to target. "
              "If omitted, this action will be performed against all clusters."
          )
          if not required
          else "One or more clusters to target",
          "nargs": "+",
          "action": UniqueSortedListAction,
          "required": required,
      }
  
      if not required:
          kwargs["default"] = CLUSTERS
  
      parser.add_argument("-c", "--clusters", **kwargs)
  
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 5 for calling a global function with example usage: add_clusters_arg(parser, required) without return types