A squeezed empty DataFrame remains a DataFrame
not_empty = pd.DataFrame([[None,None]],columns=['a', 'b']).squeeze()
type(not_empty)

empty_dim_1 = pd.DataFrame(columns=['a', 'b']).squeeze()
type(empty_dim_1)

empty_dim_0 = pd.DataFrame(index=['c', 'd']).squeeze()
type(empty_dim_0)
