迫于逻辑实在理不清了， Python 求助

{
"child": [{
"f_brandname": "奔驰",
"f_pyfirstletter": "B",
"seriesname": "载货车"
}, {
"f_brandname": "北奔重卡",
"f_pyfirstletter": "B",
"seriesname": "载货车"
}, {
"f_brandname": "福田欧曼",
"f_pyfirstletter": "F",
"seriesname": "载货车"
}, {
"f_brandname": "江铃汽车",
"f_pyfirstletter": "J",
"seriesname": "载货车"
}]
}

变成

{
"child": {
"B": [{
"f_brandname": "奔驰",
"f_pyfirstletter": "B",
"seriesname": "载货车"
}, {
"f_brandname": "北奔重卡",
"f_pyfirstletter": "B",
"seriesname": "载货车"
}],
"F": [{
"f_brandname": "福田欧曼",
"f_pyfirstletter": "F",
"seriesname": "载货车"
}],
"J": [{
"f_brandname": "江铃汽车",
"f_pyfirstletter": "J",
"seriesname": "载货车"
}]
}
}


就是把每个小字典给归类了，还有好多个品牌，这个是少数
语言是 python，求 demo，