code: def find_tokens(self, q):
      
      found_me = []
      if hasattr(self, 'location'):
        if self.location.contains(q):
          found_me = [self]
      elif self._found_by(q):
        found_me = [self]
  
      cs = [n.find_tokens(q) for n in self._children()]
      return found_me + list(itertools.chain(*cs))
docs: Find all AST nodes at the given filename, line and column.