[USER (data scientist)]:Can you count how many healthy items each chain has? Please generate and display a series to visualize the distribution of healthy menu items across popular fast food chains from the 'fastfood.csv' dataset.
 My template of code snippet is:

---BEGIN CODE TEMPLATE--- 

import pandas as pd
import pickle

# Read the fastfood data 
fastfood = pd.read_csv("fastfood.csv")  

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

print(healthy_items_by_popular_chain)
pickle.dump(healthy_items_by_popular_chain,open("./pred_result/healthy_items_by_popular_chain.pkl","wb"))

---END CODE TEMPLATE---

[YOU (AI assistant)]: Sure thing! Here's the code to count the number of healthy items offered by each popular fast food chain: 
