<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def extend_memory(self, start_position: int, size: int) -> None: """ Extend the size of the memory to be at minimum ``start_position + size`` bytes in length. Raise `eth.exceptions.OutOfGas` if there is not enough gas to pay for extending the memory. """

        validate_uint256(start_position, title="Memory start position")
        validate_uint256(size, title="Memory size")

        before_size = ceil32(len(self._memory))
        after_size = ceil32(start_position + size)

        before_cost = memory_gas_cost(before_size)
        after_cost = memory_gas_cost(after_size)

        if self.logger.show_debug2:
            self.logger.debug2(
                "MEMORY: size (%s -> %s) | cost (%s -> %s)",
                before_size,
                after_size,
                before_cost,
                after_cost,
            )

        if size:
            if before_cost < after_cost:
                gas_fee = after_cost - before_cost
                self._gas_meter.consume_gas(
                    gas_fee,
                    reason=" ".join((
                        "Expanding memory",
                        str(before_size),
                        "->",
                        str(after_size),
                    ))
                )

            self._memory.extend(start_position, size)