code: def main() -> None:
      args = argparser.parse_args()
  
      try:
          grammar, parser, tokenizer = build_parser(args.grammar_file)
      except Exception as err:
          print("ERROR: Failed to parse grammar file", file=sys.stderr)
          sys.exit(1)
  
      firs_sets = FirstSetCalculator(grammar.rules).calculate()
      pprint.pprint(firs_sets)
  
imports: import argparse
  import pprint
  import sys
  from typing import Dict, Set
  from pegen.build import build_parser
  from pegen.grammar import Alt, Cut, Gather, GrammarVisitor, Group, Lookahead, NamedItem, NameLeaf, NegativeLookahead, Opt, Repeat0, Repeat1, Rhs, Rule, StringLeaf
  from pegen.parser_generator import compute_nullables
label_desc: Use image node_id 1 for calling a global function with example usage: main() without return types