Calling 'is_valid()' removes data from the serializer

Question

When I am calling is_valid on my serializer, some of the data passed to the serializer is not getting saved. The files field is available in the serializer.initial_data, but does not get saved in serializer.validated_data. Any ideas?

Serializer:

class SomeSerializer(serializers.Serializer):
    email = serializers.EmailField()
    files = serializers.ListField(
        child=serializers.FileField()
        )

And the following view:

class SomeView(mixins.CreateModelMixin, generics.GenericAPIView):
    permission_classes = (permissions.IsAuthenticated,)
    serializer_class = SomeSerializer

    def post(self, request, *args, **kwargs):
        serializer = self.get_serializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        email = serializer.validated_data["email"]
        files = serializer.validated_data.get("files")
        #Do something here
        return response