bug: latest code breaks down the autogen.sh

[zqfan]

following https://github.com/mingrammer/diagrams/blob/master/DEVELOPMENT.md with latest commit
docker exec diagrams ./autogen.sh

error: cannot format /usr/src/diagrams/diagrams/onprem/storage.py: cannot use --safe with this file; failed to parse source file.  AST error message: can't assign to literal (<unknown>, line 19)
Oh no! 💥 💔 💥
165 files reformatted, 15 files left unchanged, 1 file failed to reformat.

vim diagrams/onprem/storage.py +19

# Aliases

{'CEPH': 'ceph', 'Ceph-OSD': 'CEPH-OSD'} = ceph