How to find subsets without itertools in Python

find_subsets.py

def find_subsets(arr) :
    result = []
    n = len(arr)
    for i in range(2**n):
        binstr = format(i, f"0{n}b")
        print(binstr)
        
        tmp = []
        for j, onebin in enumerate(binstr):
            if onebin == "1":
                tmp.append(arr[j])
                
        result.append(tmp)    
    return result