Grader is not accepting my submission even when I tested the function using the interpreter. am I missing something?

# E.g. word_count("I do not like it Sam I Am") gets back a dictionary like:
# {'i': 2, 'do': 1, 'it': 1, 'sam': 1, 'like': 1, 'not': 1, 'am': 1}
# Lowercase the string to make it easier.
def word_count(input_word):
    #Initialize an empty dictionary
    word_dict = {}

    #Lower case and split string
    word_list = input_word.lower().split(' ')

    #Iterate word list
    for word in word_list:
        #Initialize word ounter
        word_counter = 0
        #Iterate word list, comparing current word
        #with every elemen in the list word
        for index in range(len(word_list)):
            if word == word_list[index]:
                word_counter += 1
        #Update dictionary with number of occurrences
        #of the current word
        word_dict.update({word:word_counter})
    return word_dict