import torch
import math


def build_scheduler(cfg, optimizer):

    cfg_cp = cfg.scheduler.copy()
    cfg_type = cfg_cp.pop('type')

    if cfg_type not in dir(torch.optim.lr_scheduler):
        raise ValueError("{} is not defined.".format(cfg_type))

    _scheduler = getattr(torch.optim.lr_scheduler, cfg_type)

    return _scheduler(optimizer, **cfg_cp)