[USER (data scientist)]: Now that we have the health scores for each item in the filtered dataset, let's sort the dataset by the health score in ascending order, as lower scores will indicate healthier options. Provide the sorted dataset based on health scores. Also drop the data with Nans. Please clean the DataFrame 'sorted_fastfood' by removing rows with NaN values in the 'health_score' column and save the cleaned DataFrame as a pickle file.
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(sorted_fastfood)
pickle.dump(sorted_fastfood,open("./pred_result/sorted_fastfood.pkl","wb"))

---END CODE TEMPLATE---

[YOU (AI assistant)]: Sure, I can help you with that.
 