[Solved] be careful of returning 0 to filter() function.

Question

Please look at these two codes:

1️⃣ First code:

def mulof3(x):
if x % 3 == 0:
return x

m3 = list(filter(mulof3,range(10)))
print(m3)

#Outputs: [3,6,9]

2️⃣ Second code: (same task with lambda function)

m3 = list(filter(lambda n: n%3==0, range(10)))
print(m3)

#Outputs: [0,3,6,9]

🟠 Question: I can't understand why the first one doesn't output 0 in the list?
Aren't these two codes the same?