I am using modin.pandas to remove the duplicates from a dataframe.

import modin.pandas as pd
import json, ast

df = pd.DataFrame(columns=['contact_id', 'test_id'])

df['test_id'] = df['test_id'].astype(str) # Coverting test_id column data type to string
df = df.drop_duplicates(subset=['test_id', 'contact_id'], keep='first') #removing the duplicates row
df['test_id'] = df['test_id'].apply(ast.literal_eval) # converting test_id column data type to dict

I keep getting this error:

Type object 'Series' has no attribute '_get_dtypes'

Can anyone guide me how can I fix this?