Why doesn't tracemalloc show where memory is allocated when used in a Cython extension?

Question

I have a simple Cython extension that starts tracemalloc, allocates some memory, and prints the memory allocation snapshot details:

import tracemalloc

tracemalloc.start()

def test():
    arr = []
    for i in range(10000):
        arr.append(i)

    snapshot = tracemalloc.take_snapshot()
    top_stats = snapshot.statistics('traceback')
    for stat in top_stats:
        print("%s memory blocks: %.1f KiB" % (stat.count, stat.size / 1024))
        for line in stat.traceback.format():
            print(line)

However when I compile the extension and run it in the interpreter, I can't see the function names or line numbers where memory was allocated. Instead it is all combined into one <stdin> entry:

9744 memory blocks: 349.5 KiB
   File "<stdin>", line 1
13 memory blocks: 9.3 KiB
   File "<unknown>", line 0
1 memory blocks: 0.1 KiB
   File "<frozen importlib._bootstrap>", line 241

When I run the same code as a regular Python module, I can see the details:

9743 memory blocks: 266.4 KiB
  File "test.py", line 7
    for i in range(10000):
1 memory blocks: 83.1 KiB
  File "test.py", line 8
    arr.append(i)
12 memory blocks: 9.3 KiB
  File "<unknown>", line 0
1 memory blocks: 0.1 KiB
  File "test.py", line 5
    def test():

Detailed function names and line numbers are still shown for exception stack traces in Cython extensions. Why aren't they shown for the tracemalloc statistics?