@pimms.param<EOL><INDENT>def surface_coordinates(surfs):<DEDENT>
if pimms.is_map(surfs):<EOL><INDENT>return pimms.persist(surfs)<EOL><DEDENT>else:<EOL><INDENT>raise ValueError('<STR_LIT>')<EOL><DEDENT>
cortex.surface_coordinates is a mapping of the surface coordinates of the given cortex; this
must include the surfaces 'white' and 'pial'.