<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def remove_prefix(self, id):
 """ Remove a prefix from pool 'id'. """


        if 'prefix' not in request.params:
            abort(400, 'Missing prefix.')
        prefix = Prefix.get(int(request.params['prefix']))
        prefix.pool = None
        prefix.save()

        redirect(url(controller = 'pool', action = 'edit', id = id))