[USER (data scientist)]: Cool! Now, how about functions to check if an item belongs to a specific category? Please generate functions to classify items in the DataFrame 'fastfood' based on vegetarian, vegan, and gluten-free dietary preferences.
 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:

---END CODE TEMPLATE---

[YOU (AI assistant)]: Sure thing! We can create functions that check for the presence of those keywords in the item's name. Here are the functions for each category: 
 
