text: from collections import OrderedDict
  
  from rest_framework import serializers
  
  
  def remove_duplicates_from_list(data):
      return list(OrderedDict.fromkeys(data))
  
  
  class ListMultipleChoiceField(serializers.MultipleChoiceField):
      def to_internal_value(self, data):
          if isinstance(data, str) or not hasattr(data, '__iter__'):
              self.fail('not_a_list', input_type=type(data).__name__)
          if not self.allow_empty and len(data) == 0:
              self.fail('empty')
  
          internal_value_data = [
              super(serializers.MultipleChoiceField, self).to_internal_value(item)
              for item in data
          ]
  
          return remove_duplicates_from_list(internal_value_data)
  
      def to_representation(self, value):
          representation_data = [
              self.choice_strings_to_values.get(str(item), item) for item in value
          ]
  
          return remove_duplicates_from_list(representation_data)
  