code: def atom(self):
      localctx = LaTeXParser.AtomContext(self, self._ctx, self.state)
      self.enterRule(localctx, 44, self.RULE_atom)
      self._la = 0  # Token type
      try:
          self.state = 317
          self._errHandler.sync(self)
          token = self._input.LA(1)
          if token in [77, 91]:
              self.enterOuterAlt(localctx, 1)
              self.state = 295
              _la = self._input.LA(1)
              if not (_la == 77 or _la == 91):
                  self._errHandler.recoverInline(self)
              else:
                  self._errHandler.reportMatch(self)
                  self.consume()
              self.state = 308
              self._errHandler.sync(self)
              la_ = self._interp.adaptivePredict(
                  self._input, 31, self._ctx
              )
              if la_ == 1:
                  self.state = 297
                  self._errHandler.sync(self)
                  la_ = self._interp.adaptivePredict(
                      self._input, 27, self._ctx
                  )
                  if la_ == 1:
                      self.state = 296
                      self.subexpr()
  
                  self.state = 300
                  self._errHandler.sync(self)
                  la_ = self._interp.adaptivePredict(
                      self._input, 28, self._ctx
                  )
                  if la_ == 1:
                      self.state = 299
                      self.match(LaTeXParser.SINGLE_QUOTES)
  
                  pass
  
              elif la_ == 2:
                  self.state = 303
                  self._errHandler.sync(self)
                  la_ = self._interp.adaptivePredict(
                      self._input, 29, self._ctx
                  )
                  if la_ == 1:
                      self.state = 302
                      self.match(LaTeXParser.SINGLE_QUOTES)
  
                  self.state = 306
                  self._errHandler.sync(self)
                  la_ = self._interp.adaptivePredict(
                      self._input, 30, self._ctx
                  )
                  if la_ == 1:
                      self.state = 305
                      self.subexpr()
  
                  pass
  
              pass
          elif token in [78]:
              self.enterOuterAlt(localctx, 2)
              self.state = 310
              self.number()
              pass
          elif token in [76]:
              self.enterOuterAlt(localctx, 3)
              self.state = 311
              self.match(LaTeXParser.DIFFERENTIAL)
              pass
          elif token in [72]:
              self.enterOuterAlt(localctx, 4)
              self.state = 312
              self.mathit()
              pass
          elif token in [68]:
              self.enterOuterAlt(localctx, 5)
              self.state = 313
              self.frac()
              pass
          elif token in [69, 70, 71]:
              self.enterOuterAlt(localctx, 6)
              self.state = 314
              self.binom()
              pass
          elif token in [30]:
              self.enterOuterAlt(localctx, 7)
              self.state = 315
              self.bra()
              pass
          elif token in [27, 29]:
              self.enterOuterAlt(localctx, 8)
              self.state = 316
              self.ket()
              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 24 for calling the LaTeXParser obj's underlying member method code with example usage: obj.atom() and returns: localctx