from marshmallow.fields import List, ValidationError


class SelfSerializableList(list):
    def __str__(self):
        return ",".join(str(item) for item in self)


class QueryStringList(List):
    def _deserialize(self, value, attr, obj):
        """
        _deserialize handles multiple formats of query string parameter lists
        including:

        /foo?bars=1,2
        /foo?bars[]=1&bars[]2

        and returns a list of values

        """
        if value is None:
            return None

        try:
            attribute_elements = [attr_element.split(",") for attr_element in obj.getlist(attr)]
            attribute_params = SelfSerializableList(param for attr_param in attribute_elements for param in attr_param)

            return attribute_params
        except ValueError:
            raise ValidationError("Invalid query string list argument")

from marshmallow.fields import List, ValidationError


class PrintableList(list):
    def __str__(self):
        return ",".join(str(item) for item in self)


class QueryStringList(List):
    def _deserialize(self, value, attr, obj):
        """
        _deserialize handles multiple formats of query string parameter lists
        including:

        /foo?bars=1,2
        /foo?bars[]=1&bars[]2

        and returns a list of values

        """
        if value is None:
            return None

        try:
            attribute_elements = [attr_element.split(",") for attr_element in obj.getlist(attr)]
            attribute_params = PrintableList(param for attr_param in attribute_elements for param in attr_param)

            return attribute_params
        except ValueError:
            raise ValidationError("Invalid query string list argument")

Change the name of SelfSerializableList to PrintableList
Change the name of SelfSerializableList to PrintableList

  from marshmallow.fields import List, ValidationError
  
  
- class SelfSerializableList(list):
+ class PrintableList(list):
      def __str__(self):
          return ",".join(str(item) for item in self)
  
  
  class QueryStringList(List):
      def _deserialize(self, value, attr, obj):
          """
          _deserialize handles multiple formats of query string parameter lists
          including:
  
          /foo?bars=1,2
          /foo?bars[]=1&bars[]2
  
          and returns a list of values
  
          """
          if value is None:
              return None
  
          try:
              attribute_elements = [attr_element.split(",") for attr_element in obj.getlist(attr)]
-             attribute_params = SelfSerializableList(param for attr_param in attribute_elements for param in attr_param)
+             attribute_params = PrintableList(param for attr_param in attribute_elements for param in attr_param)
  
              return attribute_params
          except ValueError:
              raise ValidationError("Invalid query string list argument")
  
Change the name of SelfSerializableList to PrintableList
## Code Before:
from marshmallow.fields import List, ValidationError


class SelfSerializableList(list):
    def __str__(self):
        return ",".join(str(item) for item in self)


class QueryStringList(List):
    def _deserialize(self, value, attr, obj):
        """
        _deserialize handles multiple formats of query string parameter lists
        including:

        /foo?bars=1,2
        /foo?bars[]=1&bars[]2

        and returns a list of values

        """
        if value is None:
            return None

        try:
            attribute_elements = [attr_element.split(",") for attr_element in obj.getlist(attr)]
            attribute_params = SelfSerializableList(param for attr_param in attribute_elements for param in attr_param)

            return attribute_params
        except ValueError:
            raise ValidationError("Invalid query string list argument")

## Instruction:
Change the name of SelfSerializableList to PrintableList
## Code After:
from marshmallow.fields import List, ValidationError


class PrintableList(list):
    def __str__(self):
        return ",".join(str(item) for item in self)


class QueryStringList(List):
    def _deserialize(self, value, attr, obj):
        """
        _deserialize handles multiple formats of query string parameter lists
        including:

        /foo?bars=1,2
        /foo?bars[]=1&bars[]2

        and returns a list of values

        """
        if value is None:
            return None

        try:
            attribute_elements = [attr_element.split(",") for attr_element in obj.getlist(attr)]
            attribute_params = PrintableList(param for attr_param in attribute_elements for param in attr_param)

            return attribute_params
        except ValueError:
            raise ValidationError("Invalid query string list argument")
