How to use the bashlex.yacc.YaccSymbol function in bashlex

sym = YaccSymbol()
        sym.type = '$end'
        symstack.append(sym)
        state = 0
        while 1:
            # Get the next symbol on the input.  If a lookahead symbol
            # is already set, we just use that. Otherwise, we'll pull
            # the next token off of the lookaheadstack or from the lexer

            if not lookahead:
                if not lookaheadstack:
                    lookahead = get_token()     # Get the next token
                else:
                    lookahead = lookaheadstack.pop()
                if not lookahead:
                    lookahead = YaccSymbol()
                    lookahead.type = '$end'

            # Check the action table
            ltype = lookahead.type
            t = actions[state].get(ltype)

            if t is not None:
                if t > 0:
                    # shift a symbol on the stack
                    statestack.append(t)
                    state = t

                    symstack.append(lookahead)
                    lookahead = None

                    # Decrease error count on successful shift

sym = YaccSymbol()
        sym.type = '$end'
        symstack.append(sym)
        state = 0
        while 1:
            # Get the next symbol on the input.  If a lookahead symbol
            # is already set, we just use that. Otherwise, we'll pull
            # the next token off of the lookaheadstack or from the lexer

            if not lookahead:
                if not lookaheadstack:
                    lookahead = get_token()     # Get the next token
                else:
                    lookahead = lookaheadstack.pop()
                if not lookahead:
                    lookahead = YaccSymbol()
                    lookahead.type = '$end'

            # Check the action table
            ltype = lookahead.type
            t = actions[state].get(ltype)

            if t is not None:
                if t > 0:
                    # shift a symbol on the stack
                    statestack.append(t)
                    state = t

                    symstack.append(lookahead)
                    lookahead = None

                    # Decrease error count on successful shift

get_token = tokenfunc

        # Set up the state and symbol stacks

        statestack = [ ]                # Stack of parsing states
        self.statestack = statestack
        symstack   = [ ]                # Stack of grammar symbols
        self.symstack = symstack

        pslice.stack = symstack         # Put in the production
        errtoken   = None               # Err token

        # The start state is assumed to be (0,$end)

        statestack.append(0)
        sym = YaccSymbol()
        sym.type = '$end'
        symstack.append(sym)
        state = 0
        while 1:
            # Get the next symbol on the input.  If a lookahead symbol
            # is already set, we just use that. Otherwise, we'll pull
            # the next token off of the lookaheadstack or from the lexer

            if not lookahead:
                if not lookaheadstack:
                    lookahead = get_token()     # Get the next token
                else:
                    lookahead = lookaheadstack.pop()
                if not lookahead:
                    lookahead = YaccSymbol()
                    lookahead.type = '$end'

# case 2: the statestack has a couple of entries on it, but we're
                # at the end of the file. nuke the top entry and generate an error token

                # Start nuking entries on the stack
                if lookahead.type == '$end':
                    # Whoa. We're really hosed here. Bail out
                    return

                if lookahead.type != 'error':
                    sym = symstack[-1]
                    if sym.type == 'error':
                        # Hmmm. Error is on top of stack, we'll just nuke input
                        # symbol and continue
                        lookahead = None
                        continue
                    t = YaccSymbol()
                    t.type = 'error'
                    if hasattr(lookahead,"lineno"):
                        t.lineno = lookahead.lineno
                    t.value = lookahead
                    lookaheadstack.append(lookahead)
                    lookahead = t
                else:
                    symstack.pop()
                    statestack.pop()
                    state = statestack[-1]       # Potential bug fix

                continue

            # Call an error function here
            raise RuntimeError("yacc: internal parser error!!!\n")

symstack.append(lookahead)
                    lookahead = None

                    # Decrease error count on successful shift
                    if errorcount: errorcount -=1
                    continue

                if t < 0:
                    # reduce a symbol on the stack, emit a production
                    p = prod[-t]
                    pname = p.name
                    plen  = p.len
                    accept = False

                    # Get production function
                    sym = YaccSymbol()
                    sym.type = pname       # Production name
                    sym.value = None

                    if plen:
                        targ = symstack[-plen-1:]
                        targ[0] = sym

                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
                        # The code enclosed in this section is duplicated 
                        # below as a performance optimization.  Make sure
                        # changes get made in both locations.

                        pslice.slice = targ
                        
                        try:
                            # Call the grammar rule with our special slice object

symstack.append(lookahead)
                    lookahead = None

                    # Decrease error count on successful shift
                    if errorcount: errorcount -=1
                    continue

                if t < 0:
                    # reduce a symbol on the stack, emit a production
                    p = prod[-t]
                    pname = p.name
                    plen  = p.len
                    accept = False

                    # Get production function
                    sym = YaccSymbol()
                    sym.type = pname       # Production name
                    sym.value = None

                    # --! DEBUG
                    if plen:
                        debug.info("Action : Reduce rule [%s] with %s and goto state %d", p.str, "["+",".join([format_stack_entry(_v.value) for _v in symstack[-plen:]])+"]",-t)
                    else:
                        debug.info("Action : Reduce rule [%s] with %s and goto state %d", p.str, [],-t)
                        
                    # --! DEBUG

                    if plen:
                        targ = symstack[-plen-1:]
                        targ[0] = sym

                        # --! TRACKING

# Get the next symbol on the input.  If a lookahead symbol
            # is already set, we just use that. Otherwise, we'll pull
            # the next token off of the lookaheadstack or from the lexer

            # --! DEBUG
            debug.debug('')
            debug.debug('State  : %s', state)
            # --! DEBUG

            if not lookahead:
                if not lookaheadstack:
                    lookahead = get_token()     # Get the next token
                else:
                    lookahead = lookaheadstack.pop()
                if not lookahead:
                    lookahead = YaccSymbol()
                    lookahead.type = "$end"

            # --! DEBUG
            debug.debug('Stack  : %s',
                        ("%s . %s" % (" ".join([xx.type for xx in symstack][1:]), str(lookahead))).lstrip())
            # --! DEBUG

            # Check the action table
            ltype = lookahead.type
            t = actions[state].get(ltype)

            if t is not None:
                if t > 0:
                    # shift a symbol on the stack
                    statestack.append(t)
                    state = t

# case 2: the statestack has a couple of entries on it, but we're
                # at the end of the file. nuke the top entry and generate an error token

                # Start nuking entries on the stack
                if lookahead.type == '$end':
                    # Whoa. We're really hosed here. Bail out
                    return

                if lookahead.type != 'error':
                    sym = symstack[-1]
                    if sym.type == 'error':
                        # Hmmm. Error is on top of stack, we'll just nuke input
                        # symbol and continue
                        lookahead = None
                        continue
                    t = YaccSymbol()
                    t.type = 'error'
                    if hasattr(lookahead,"lineno"):
                        t.lineno = lookahead.lineno
                    t.value = lookahead
                    lookaheadstack.append(lookahead)
                    lookahead = t
                else:
                    symstack.pop()
                    statestack.pop()
                    state = statestack[-1]       # Potential bug fix

                continue

            # Call an error function here
            raise RuntimeError("yacc: internal parser error!!!\n")