How can I make a function with a dictionary of occurrences from list I set later?

I have a set of functions that are meant to set a dictionary with the key being the character that occurs in the lists and the items being the number of occurrences but when I run the code the dictionary is empty.

This is my actual code

def uniqueOccurrence(item1, item2, item3):
    d = {}
    for i in d:
        if i in d:
            d[i] = d[i] + 1
        else:
            d[i] = 1
    return d
    
def main():
    list1 = [1]
    list2 = [1,2]
    list3 = [1,2,3]
    
    print(uniqueOccurrence(list1, list2, list3))
    
if __name__ == "__main__":
    main()

It is supposed to return something like this
{1: 3, 2: 2, 3: 1}

but is returning an empty dictionary
{}

You do not use your input parameters in the function, you can do it like this:

def count_elements(*lists):
    element_count = {}
    for lst in lists:
        for element in lst:
            if element in element_count:
                element_count[element] += 1
            else:
                element_count[element] = 1
    return element_count

count_elements(list1, list2, list3)

Or use a Counter:

from collections import Counter

def count_elements(*lists):
    element_count = Counter()
    for lst in lists:
        element_count.update(lst)
    return element_count

count_elements(list1, list2, list3)