如何将包含字典值的字典转换为以这些值的键为列的pandas DataFrame

import pandas as pd

data = {
    'key1': {'subkey1': 'value1', 'subkey2': 'value2'},
    'key2': {'subkey1': 'value3', 'subkey2': 'value4'}
}

df = pd.DataFrame.from_dict(data, orient='index')

df = df.apply(lambda x: pd.Series(x))

import pandas as pd

data = {
    'key1': {'subkey1': 'value1', 'subkey2': 'value2'},
    'key2': {'subkey1': 'value3', 'subkey2': 'value4'}
}

df = pd.DataFrame.from_dict(data, orient='index')
df = df.apply(lambda x: pd.Series(x))