old_contents: from mmcv.runner import obj_from_dict
  
  from .random_sampler import RandomSampler
  from ..assign_sampling import build_sampler
  
  
  class CombinedSampler(RandomSampler):
  
      def __init__(self, num, pos_fraction, pos_sampler, neg_sampler, **kwargs):
          super(CombinedSampler, self).__init__(num, pos_fraction, **kwargs)
          default_args = dict(num=num, pos_fraction=pos_fraction)
          default_args.update(kwargs)
          self.pos_sampler = build_sampler(
              pos_sampler, default_args=default_args)
          self.neg_sampler = build_sampler(
              neg_sampler, default_args=default_args)
  
new_contents: from .random_sampler import RandomSampler
  from ..assign_sampling import build_sampler
  
  
  class CombinedSampler(RandomSampler):
  
      def __init__(self, num, pos_fraction, pos_sampler, neg_sampler, **kwargs):
          super(CombinedSampler, self).__init__(num, pos_fraction, **kwargs)
          default_args = dict(num=num, pos_fraction=pos_fraction)
          default_args.update(kwargs)
          self.pos_sampler = build_sampler(
              pos_sampler, default_args=default_args)
          self.neg_sampler = build_sampler(
              neg_sampler, default_args=default_args)
  
subject: remove unused imports