testing: Django Test - Send Array of Arrays containing Integer

currently i am trying to send an array of arrays containing integers to my rest api, this is part of my test:

res = self.client.post(
    '/data',
    {
        'data': [
            [1,2,3],
            [4,5,6]
        ]
    }
)

In my serializer i try to print the data:

def create(self, validated_data):
    print(self.context['request'].data)
    print(self.context['request'].data['data'])

But i just get:

<QueryDict: {'data': ['[1, 2, 3]', '[4, 5, 6]']}>
[4, 5, 6]

Expected:

{'data': [[1, 2, 3], [4, 5, 6]]}
[[1, 2, 3], [4, 5, 6]]

How can this be?

Did i send the wrong format or did i access the json the wrong way...?

Thanks and Greetings!

testing