import pandas as pd

# create a sample dataframe
df = pd.DataFrame({'col1': ['a', 'b', 'c', 'a', 'b', 'a'],
                   'col2': ['x', 'y', 'z', 'x', 'y', 'x']})

# get the frequency of unique values in the entire dataframe
value_counts = df.stack().value_counts()

print(value_counts)