[USER (data scientist)]: Hey Tapilot, I'm working on this atp_tennis dataset and I could use a hand. Can you help me figure out if there are any missing values or weird data stuff going on? Please generate the code with the output in series type.
My template of code snippet is:

---BEGIN CODE TEMPLATE---

import pandas as pd
import pickle
from decision_company import read_csv_file, sum_up, is_null, n_unique, create_dataframe

atp_tennis = read_csv_file('atp_tennis.csv')

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

print(missing_values)

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

---END CODE TEMPLATE---

[YOU (AI assistant)]: No problem, happy to help! Let's start by finding any missing values in the dataset. Here's some code for that: 

# MY SOLUTION BEGIN:
