def _tgrep_parens_action(_s, _l, tokens):
 assert (len(tokens) == 3)
 assert (tokens[0] == u'(')
 assert (tokens[2] == u')')
 return tokens[1]

def _tgrep_parens_action ( _s , _l , tokens ) : assert ( len ( tokens ) == 3 ) assert ( tokens [ 0 ] == u'(' ) assert ( tokens [ 2 ] == u')' ) return tokens [ 1 ]
builds a lambda function representing a predicate on a tree node from a parenthetical notation .