<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_validator_change(cls, bigchain):
 """Return the validator set from the most recent approved block :return: { 'height': <block_height>, 'validators': <validator_set> } """

        latest_block = bigchain.get_latest_block()
        if latest_block is None:
            return None
        return bigchain.get_validator_change(latest_block['height'])