[USER (data scientist)]: Hey Tapilot, I have this dataset of tennis matches, and I want to update the odds for each match based on the new competitors' performance. Can you help me figure out the head-to-head win rates for each player? Please generate the code with the output in function type.
My template of code snippet is:

---BEGIN CODE TEMPLATE---

import pandas as pd
import numpy as np
import pickle
from decision_company import read_csv_file, concatenate_objects, create_dataframe, bind_dataframe, reset_index, rename_columns, access_dataframe_loc, join_dataframes, get_max, assert_series, extract_unique_values, is_a_null_df, visit_by_index, fetch_df_size, iterate_rows

# Load the dataset 
atp_tennis = read_csv_file('atp_tennis.csv')

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

---END CODE TEMPLATE---

[YOU (AI assistant)]: Absolutely! Here's a function that calculates the head-to-head win rates for each player in your dataset: 

# MY SOLUTION BEGIN:
