@pimms.param<EOL><INDENT>def chirality(ch):<DEDENT>
ch = to_hemi_str(ch)<EOL>if ch == '<STR_LIT>': return None<EOL>else: return ch<EOL>
proj.chirality is either 'lh', 'rh', or None, and specifies whether the given map projection
is valid only for LH or RH chiralities; None indicates that the projection does not care
about chirality.