text: from eth.constants import SECPK1_N
  
  NULL_ADDRESS: str = "0x" + "0" * 40
  SENTINEL_ADDRESS: str = "0x" + "0" * 39 + "1"
  
  # keccak('Transfer(address,address,uint256)')
  ERC20_721_TRANSFER_TOPIC: str = (
      "0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef"
  )
  
  SIGNATURE_R_MIN_VALUE: int = 1
  SIGNATURE_R_MAX_VALUE: int = SECPK1_N - 1
  SIGNATURE_S_MIN_VALUE: int = 1
  SIGNATURE_S_MAX_VALUE: int = SECPK1_N // 2
  SIGNATURE_V_MIN_VALUE: int = 27
  SIGNATURE_V_MAX_VALUE: int = 28
  
  
  GAS_CALL_DATA_ZERO_BYTE = 4
  GAS_CALL_DATA_BYTE = 16  # 68 before Istanbul
  