code: def group(self):
      localctx = LaTeXParser.GroupContext(self, self._ctx, self.state)
      self.enterRule(localctx, 38, self.RULE_group)
      try:
          self.state = 267
          self._errHandler.sync(self)
          token = self._input.LA(1)
          if token in [19]:
              self.enterOuterAlt(localctx, 1)
              self.state = 251
              self.match(LaTeXParser.L_PAREN)
              self.state = 252
              self.expr()
              self.state = 253
              self.match(LaTeXParser.R_PAREN)
              pass
          elif token in [25]:
              self.enterOuterAlt(localctx, 2)
              self.state = 255
              self.match(LaTeXParser.L_BRACKET)
              self.state = 256
              self.expr()
              self.state = 257
              self.match(LaTeXParser.R_BRACKET)
              pass
          elif token in [21]:
              self.enterOuterAlt(localctx, 3)
              self.state = 259
              self.match(LaTeXParser.L_BRACE)
              self.state = 260
              self.expr()
              self.state = 261
              self.match(LaTeXParser.R_BRACE)
              pass
          elif token in [23]:
              self.enterOuterAlt(localctx, 4)
              self.state = 263
              self.match(LaTeXParser.L_BRACE_LITERAL)
              self.state = 264
              self.expr()
              self.state = 265
              self.match(LaTeXParser.R_BRACE_LITERAL)
              pass
          else:
              raise NoViableAltException(self)
  
      except RecognitionException as re:
          localctx.exception = re
          self._errHandler.reportError(self, re)
          self._errHandler.recover(self, re)
      finally:
          self.exitRule()
      return localctx
  
imports: from antlr4 import *
  from io import StringIO
  import sys
label_desc: Use image node_id 21 for calling the LaTeXParser obj's underlying member method code with example usage: obj.group() and returns: localctx