code: def _update_undefined(self, symbols):
      self.undefined.update(symbols - self._stable_lhs)
  
imports: from __future__ import print_function
  from __future__ import division
  from __future__ import absolute_import
  from ..visitors import Visitor, visit_children
  from ..visitors.symbol_visitor import get_symbols
  import ast
  from ...utils import py2op
label_desc: Use image node_id 6 for calling the ConditionalSymbolVisitor obj's underlying member method code with example usage: obj._update_undefined(symbols) without return types