class_docstr: Subclass of argparse._AppendAction to avoid multiple of the same choice from a list of files
  
  This is meant to augment the 'append' argparse action
class_docstr_tok: ["Subclass","of","argparse._AppendAction","to","avoid","multiple","of","the","same","choice","from","a","list","of","files","This","is","meant","to","augment","the","'append","'","argparse","action"]
code: def __call__(self, parser, namespace, value, option_string=None):
      unique_items = set(getattr(namespace, self.dest, set()))
      unique_items.add(value.name)
      setattr(namespace, self.dest, sorted(unique_items))
  
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 1 for calling the UniqueSortedFileListAppendAction obj's underlying member method code with example usage: obj.__call__(parser, namespace, value, option_string) without return types