def verify_input_sig_for_legacy(input_index, script_pubkey, flags)
      script_sig = inputs[input_index].script_sig
      checker = Bitcoin::TxChecker.new(tx: self, input_index: input_index)
      interpreter = Bitcoin::ScriptInterpreter.new(checker: checker, flags: flags)

      interpreter.verify_script(script_sig, script_pubkey)
    end
def verify_input_sig_for_legacy(input_index, script_pubkey, flags)
      script_sig = inputs[input_index].script_sig
      checker = Bitcoin::TxChecker.new(tx: self, input_index: input_index)
      interpreter = Bitcoin::ScriptInterpreter.new(checker: checker, flags: flags)

      interpreter.verify_script(script_sig, script_pubkey)
    end
verify input signature for legacy tx.