@classmethod<EOL><INDENT>def _get_ax_layer(cls, ax, primary=True):<DEDENT>
if primary:<EOL><INDENT>return getattr(ax, '<STR_LIT>', ax)<EOL><DEDENT>else:<EOL><INDENT>return getattr(ax, '<STR_LIT>', ax)<EOL><DEDENT>
get left (primary) or right (secondary) axes