code: def visit_Rhs(self, item: Rhs) -> Set[str]:
      result: Set[str] = set()
      for alt in item.alts:
          result |= self.visit(alt)
      return result
  
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 15 for calling the FirstSetCalculator obj's underlying member method code with example usage: obj.visit_Rhs(item) and returns: result