Split a JSON file in python

I have a JSON file like this :

{"1012.jpg": [[122, 232], [108, 127], [31, 86]],
"1890.jpg": [[172, 234], [162, 146], [154, 81]],
"2544.jpg": [[53, 232], [37, 175], [6, 150]],
...
"1591.jpg": [[173, 236], [155, 129], [194, 84]],
"2570.jpg": [[45, 234], [28, 181], [4, 135]],
"1927.jpg": [[162, 230], [155, 144], [154, 76]]}

I would like to split this JSON file in Python within 3 files.

I tried to convert the JSON file into pandas dataframe : in doing :

df = pd.read_json("labels.json")
row, column = df.shape
cols = df.columns.tolist()
partage = 2
colsTest = cols[:int(np.round(column/partage))]
colsTrain = cols[int(np.round(column/partage)):]

dfTrain = df[colsTrain]
dfTest = df[colsTest]

print(dfTrain.to_json(orient='index'))

But I miss other datas :

{"0":{"2178.jpg":[171,232],"2179.jpg":[169,235],"218.jpg": 
[143,232],"2180.jpg":[169,233],"2181.jpg":[160,234],"2182.jpg":
...
"993.jpg":[42,82],"994.jpg":[39,84],"995.jpg":[34,82],"996.jpg": 
[37,84],"997.jpg":[37,83],"998.jpg":[47,84],"999.jpg":[45,86]}

How can I do that ?