MAINT: clean up and improve docs.
BUG: fix imports.
MAINT: refactor test.
MAINT: change class name.
MAINT: remove error since won't be reached.
TST: improve and expand tests.
MAINT: change class name.
MAINT: change class name.
MAINT: extract string constants and remove error that won't be reached.
STY: fix line length.
MAINT: undo name change.