[Python] Transform 2-level nested dictonary to list of dictionaries [duplicate]

I have the following nested dictionary:

d = {
'1': {'2': [1, 1, 1, 1, 1],
'3': [2, 2, 2, 2, 2],
'4': [4, 4, 4, 4, 4]},
'2': {'3': [3, 3, 3, 3, 3],
'5': [5, 5, 5, 5, 5]}
}


I want to "flatten" this dictionary and obtain the following output:

l = [{'u': 1, 'v': 2, 'k': [1, 1, 1, 1, 1]},
{'u': 1, 'v': 3, 'k': [2, 2, 2, 2, 2]},
{'u': 2, 'v': 3, 'k': [3, 3, 3, 3, 3]},
{'u': 1, 'v': 4, 'k': [4, 4, 4, 4, 4]},
{'u': 2, 'v': 5, 'k': [5, 5, 5, 5, 5]}]


Ideally, I would like to use itertools. The following code works but I would like to know if there is room for improvement.

from itertools import chain

l = chain.from_iterable([[
{'u': u,
'v': v,
'k': d[v]
} for v in d.keys()
] for u in d.keys()

])


Please advice

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