Black fails when using sizeof

[cphyc]

Describe the bug

Black fails on a simple cython file which uses sizeof.

To Reproduce

1. Create the file

# file.pyx
cdef INT32_SIZE = sizeof(int)

2. Apply black on it:

$ black -t cython file.pyx
error: cannot format file.pyx: Cannot parse: 12:5: cdef INT32_SIZE = sizeof(np.int32_t)
Oh no! 💥 💔 💥
1 file failed to reformat.

Expected behavior
This should not fail as this is a valid cython file.

Environment (please complete the following information):

• Operating System and Version: ArchLinux, Python 3.9.2, black 19.3b0 (downloaded from the cython_support branch).