def estimate_tx_operational_gas(self, safe_address: str, data_bytes_length: int):
threshold = self.retrieve_threshold(safe_address)<EOL>return <NUM_LIT> + data_bytes_length // <NUM_LIT:32> * <NUM_LIT:100> + <NUM_LIT> * threshold<EOL>
Estimates the gas for the verification of the signatures and other safe related tasks
before and after executing a transaction.
Calculation will be the sum of:
  - Base cost of 15000 gas
  - 100 of gas per word of `data_bytes`
  - Validate the signatures 5000 * threshold (ecrecover for ecdsa ~= 4K gas)
:param safe_address: Address of the safe
:param data_bytes_length: Length of the data (in bytes, so `len(HexBytes('0x12'))` would be `1`
:return: gas costs per signature * threshold of Safe