[USER (data scientist)]: Awesome, thanks! Now, I wanna know how many unique values there are for a few columns like Tournament, Series, Court, Surface, and Round. Can you help me out with that? Please generate a Series summarizing the unique value counts for selected columns in this dataset.
My template of code snippet is:

---BEGIN CODE TEMPLATE---

import pandas as pd
import pickle

atp_tennis = pd.read_csv('atp_tennis.csv')

# YOUR SOLUTION BEGIN:
<code1>
[COMPLETE YOUR CODE] 
</code1>
# YOUR SOLUTION END

str(unique_values)

# save data
pickle.dump(unique_values,open("./pred_result/unique_values.pkl","wb"))

---END CODE TEMPLATE---

[YOU (AI assistant)]: You got it! Here's the code to find the unique values for those columns: 
'''
import pandas as pd
import pickle

atp_tennis = pd.read_csv('atp_tennis.csv')

# YOUR SOLUTION BEGIN:
