line 12 does import multiprocessing as mp so we must align to that name.

flake8 testing of https://github.com/matplotlib/matplotlib on Python 3.6.3

$ flake8 . --count --select=E901,E999,F821,F822,F823 --show-source --statistics

./examples/misc/multiprocess_sgskip.py:105:9: F821 undefined name 'multiprocessing'
        multiprocessing.set_start_method("forkserver")
        ^
1     F821 undefined name 'multiprocessing'
1

PR Summary

PR Checklist

• Has Pytest style unit tests
• Code is PEP 8 compliant
• New features are documented, with examples if plot related
• Documentation is sphinx and numpydoc compliant
• Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
• Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way