          self.queryset = kwargs.pop('queryset', None)
          self.null = kwargs.pop('null', False)
          super(RelatedField, self).__init__(*args, **kwargs)
          self.read_only = kwargs.pop('read_only', self.default_read_only)
          if self.many:
              self.widget = self.many_widget
  
 
</s> remove             value = data[field_name]
 </s> add             if self.many:
                try:
                    # Form data
                    value = data.getlist(field_name)
                    if value == ['']:
                        value = []
                except AttributeError:
                    # Non-form data
                    value = data[field_name]
            else:
                value = data[field_name]
        self.many = kwargs.pop('many', self.many)
          self.queryset = kwargs.pop('queryset', None)
          self.null = kwargs.pop('null', False)
        self.many = kwargs.pop('many', self.many)
          super(RelatedField, self).__init__(*args, **kwargs)
          self.read_only = kwargs.pop('read_only', self.default_read_only)
          if self.many:
              self.widget = self.many_widget
  
keep add keep keep keep keep keep
 Starting migration from ManyField to Field(many=True) 
rest_framework/relations.py