code: def is_generator(self, node):
          
          results = {}
          if self.yield_expr.match(node, results):
              return True
          for child in node.children:
              if child.type not in (syms.funcdef, syms.classdef):
                  if self.is_generator(child):
                      return True
          return False
docs: Traverse the tree below node looking for 'yield [expr]'.