<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_ops(self, key):
        ''' Returns ops from the key if found otherwise raises a KeyError.
        '''
        ops = self._store.get(key)
        if ops is None:
            raise KeyError(
                'cannot get operations for {}'.format(key))
        return ops