def _valid_size(size):
 if ((size % 1024) == 0):
  return (True, '')
 return (False, ('Filesystem size must be multiple of 1024, not %d' % (size,)))

def _valid_size ( size ) : if ( ( size % 1024 ) == 0 ) : return ( True , '' ) return ( False , ( 'Filesystem size must be multiple of 1024, not %d' % ( size , ) ) )
pyrsistent invariant for filesystem size .