code: def visitSetComp(self, node):
      defined, required = self.handle_generators(node.generators)
      required.update(get_symbols(node.elt, _ast.Load) - defined)
  
      for symbol in required:
          if not self.graph.has_node(symbol):
              self.graph.add_node(symbol)
              self.undefined.add(symbol)
  
      return required
  
imports: from __future__ import print_function
  from __future__ import division
  from __future__ import absolute_import
  from ...asttools import Visitor, visit_children
  import _ast
  from ...asttools.visitors.symbol_visitor import get_symbols
label_desc: Use image node_id 8 for calling the CollectNodes obj's underlying member method code with example usage: obj.visitSetComp(node) and returns: required