code: def ket(self):
      localctx = LaTeXParser.KetContext(self, self._ctx, self.state)
      self.enterRule(localctx, 48, self.RULE_ket)
      self._la = 0  # Token type
      try:
          self.enterOuterAlt(localctx, 1)
          self.state = 323
          _la = self._input.LA(1)
          if not (_la == 27 or _la == 29):
              self._errHandler.recoverInline(self)
          else:
              self._errHandler.reportMatch(self)
              self.consume()
          self.state = 324
          self.expr()
          self.state = 325
          self.match(LaTeXParser.R_ANGLE)
      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 26 for calling the LaTeXParser obj's underlying member method code with example usage: obj.ket() and returns: localctx