• No need to convert input_args to lists: broadcast_arrays will handle
  the broadcasting just fine on scalars, and later using np.ravel() will
  ensure that the result is at least 1D.
• The assertions don't really add much (and are clearly always true
  based on the code just above).
• np.linspace(x, y, 2) is a pretty obfuscated way to write np.array([x,
  y]).

PR Summary

PR Checklist

• Has Pytest style unit tests
• Code is Flake 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