old_contents: from __future__ import absolute_import
  
  from .base import BaseDataset
  
  class SimpleDataset(BaseDataset):
      def __init__(self, queryset, headers=None):
          self.queryset = queryset
          if headers is None:
              fields = queryset.model._meta.fields
              self.header_list = [field.name for field in fields]
              self.attr_list = self.header_list
          elif type(headers) is dict:
              self.header_dict = headers
              self.header_list = self.header_dict.keys()
              self.attr_list = self.header_dict.values()
          elif type(headers) is list:
              self.header_list = headers
              self.attr_list = headers
          super(SimpleDataset, self).__init__()
  
  
new_contents: from __future__ import absolute_import
  
  from .base import BaseDataset
  
  class SimpleDataset(BaseDataset):
      def __init__(self, queryset, headers=None):
          self.queryset = queryset
          if headers is None:
              fields = queryset.model._meta.fields
              self.header_list = [field.name for field in fields]
              self.attr_list = self.header_list
          elif isinstance(headers, dict):
              self.header_dict = headers
              self.header_list = self.header_dict.keys()
              self.attr_list = self.header_dict.values()
          elif isinstance(headers, list):
              self.header_list = headers
              self.attr_list = headers
          super(SimpleDataset, self).__init__()
  
  
subject: Use isinstance to check type