code: def handle_open_group(s, state):
      if s[0] == "(":
          if len(s) > 2 and s[1] == "?":
              if s[2] in ("=", "!", ":"):
                  # a look-ahead expression or parentheses without grouping
                  state.open_group(3, is_non_grouping=True)
                  return 3
              elif len(s) > 3 and s[1:3] == "<=":
                  # A look-ahead expression
                  state.open_group(4, is_non_grouping=True)
                  return 4
              elif s[2] in set("iLmsux"):
                  # Setting switches
                  match = re.match(r"\(\?[iLmsux]+\)", s)
                  if not match:
                      raise ValueError(
                          "Incomplete or badly formatted switch expression"
                      )
                  state.parsed_special(len(match.group()))
                  return len(match.group())
              elif s[2] == "#":
                  # comment
                  match = re.match(r"\(\?#.*\)", s)
                  if not match:
                      raise ValueError(
                          "Incomplete or badly formatted comment"
                      )
                  state.parsed_special(len(match.group()))
                  return len(match.group())
              elif s[2] == "(":
                  # (?(name/id)) construct
                  match = re.match(r"\(\?\(([^)]+)\)", s)
                  if not match:
                      raise ValueError(
                          "Incomplete or badly formatted conditional match"
                      )
                  name_or_id = match.group(1)
                  if name_or_id.isdigit():
                      if int(name_or_id) > state.group_count:
                          raise ValueError(
                              "Not enough groups before conditional match: asked for %d, but only %d available"
                              % (int(name_or_id), state.group_count)
                          )
                  else:
                      if not state.is_group_name(name_or_id):
                          raise ValueError(
                              'Unavailable group name, "%s", in conditional match'
                              % name_or_id
                          )
                  state.open_group(
                      len(match.group()), is_non_grouping=True
                  )
              elif s[2] == "P" and len(s) > 3:
                  if s[3] == "=":
                      # (?P=FOO) matches the previous group expression, FOO
                      match = re.match(r"\(\?P=([^)]+)\)", s)
                      if not match:
                          raise ValueError(
                              "Incomplete or badly formatted named group reference"
                          )
                      else:
                          state.parsed_token(
                              len(match.group()), TOK_GROUP
                          )
                          return len(match.group())
                  elif s[3] == "<":
                      # Named group definition: (?P<FOO>...)
                      match = re.match(r"\(\?P<([^>]+)>", s)
                      if not match:
                          raise ValueError(
                              "Incomplete or badly formattted named group definition"
                          )
                      elif state.is_group_name(match.group(1)):
                          raise ValueError(
                              "Doubly-defined group: %s"
                              % match.group(1)
                          )
                      else:
                          group_name = match.group(1)
                          state.open_group(
                              len(match.group()),
                              group_name=group_name,
                              is_non_grouping=True,
                          )
                          state.token_labels[
                              -len(group_name) - 1 : -1
                          ] = [
                              TOK_DEFINITION
                              + state.group_name_index(group_name)
                          ] * len(
                              group_name
                          )
                          return len(match.group())
                  else:
                      raise ValueError(
                          "Incomplete or badly formatted (?P expression"
                      )
              else:
                  raise ValueError(
                      "Incomplete or badly formatted (? expression"
                  )
          else:
              state.open_group(1)
              return 1
  
imports: import re
  import wx
  import wx.stc
label_desc: Use image node_id 4 for calling a global function with example usage: handle_open_group(s, state) and returns: int, int, int, len, len, len, len