docstr: Open a grouping expression
code: def open_group(self, length, group_name=None, is_non_grouping=False):
      """Open a grouping expression"""
      self.__group_depth += 1
      self.__group_starts.append(self.position)
      self.__any_tokens = True
      self.__group_name = group_name
      self.__is_non_grouping = is_non_grouping
      self.__any_tokens = False
      self.mark_tokens(length, TOK_GROUP)
      self.position += length
  
imports: import re
  import wx
  import wx.stc
label_desc: Use image node_id 3 for calling the RegexpState obj's underlying member method code with example usage: obj.open_group(length, group_name, is_non_grouping) without return types