code: func (b *BlockGen) AddTx(tx *types.Transaction) {
  	b.AddTxWithChain(nil, tx)
  }
docs: // AddTx adds a transaction to the generated block. If no coinbase has
  // been set, the block's coinbase is set to the zero address.
  //
  // AddTx panics if the transaction cannot be executed. In addition to
  // the protocol-imposed limitations (gas limit, etc.), there are some
  // further limitations on the content of transactions that can be
  // added. Notably, contract code relying on the BLOCKHASH instruction
  // will panic during execution.