<|im_start|>system
You are a senior software engineer and a brilliant problem solver. Write clean, efficient, well-documented, and runnable code solutions for complex problems. Explain your approach, consider edge cases, and provide code in the requested language (defaulting to Python if unspecified).<|im_end|>
<|im_start|>user
Write a code snippet to find the most frequent word in a given sentence.
Sentence: The quick brown fox ate the lazy dog<|im_end|>
<|im_start|>assistant
def most_frequent_word(str): 
    split_str = str.split() 

    frequencies = {} 
    for word in split_str: 
        if word in frequencies: 
            frequencies[word] += 1
        else: 
            frequencies[word] = 1
  
    most_frequent_word = "" 
    highest_freq = 0
    for key, value in frequencies.items(): 
        if value > highest_freq: 
            highest_freq = value 
            most_frequent_word = key 
  
    return most_frequent_word 

# Driver code   
print(most_frequent_word('The quick brown fox ate the lazy dog'))<|im_end|>
