@pimms.param<EOL><INDENT>def chirality(ch):<DEDENT>
if ch is None: return None<EOL>ch = ch.lower()<EOL>if ch != '<STR_LIT>' and ch != '<STR_LIT>':<EOL><INDENT>raise ValueError('<STR_LIT>')<EOL><DEDENT>return ch<EOL>
topo.chirality gives the chirality ('lh' or 'rh') for the given topology; this may be None
if no chirality has been specified.