matplotlib Code

Another pass at fixing simplification.

[3058804] part of a line is not drawn

cleanup previous commit.

deleting an item from parallels/meridians dict removes it from plot.

don't raise exception if parallel or meridian already removed.

reconsider removeparallels and removemeridians. Add remove method to tuples contained
in dicts returned by drawparallels and drawmeridians instead.

make removemeridians, removeparallels work interactively

Add link in docstring.

add removeparallels and removemeridians convenience methods.

figure.py, axes tracking: ensure a unique key is provided.