Pandas dataframe with multiple observations per model
# create the df
df = pd.DataFrame({'model':['our','theirs'],'metric':['acc','sen'],'value':[np.array([1,2,3]),np.array([4,5,6])]})
# unzip the array into three columns
df[['ex1','ex2','ex3']]=pd.DataFrame(df['value'].to_list(),index=df.index)
# melt df to long df
df.melt(id_vars=['model','metric'],value_vars=['ex1','ex2','ex3'])


You may need to sort the dataframe as you like.