PR Summary

Closes #11515

Don't mess with the user-supplied dictionaries in subplots...

Dunno if this really merits a test..

import numpy as np
import matplotlib.pyplot as plt


subplot_kw = {'sharex': 'all'}
print(subplot_kw)
fig, ax = plt.subplots(2, 1, subplot_kw=subplot_kw)
print(subplot_kw)

New:

{'sharex': 'all'}
{'sharex': 'all'}

Old:

{'sharex': 'all'}
{'sharex': None, 'sharey': None}

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