def __init__(self, mainsym, unkmthd = None, symtab = None):
        '''
        Construct a page macro expander.

        @param mainsym: Main symbol to be displayed.
        @type mainsym: str
        @param unkmthd: Resolution method of undefined symbols
        (C{PageMacro.KEEPMODE} or C{PageMacro.DELMODE}).
        @type unkmthd: int
        @param symtab: Symbol table.
        @type symtab: dict
        '''

        if unkmthd is None: unkmthd = PageMacro.KEEPMODE
        if symtab is None: symtab = {}

        self.mainsym = mainsym
        self.unkmthd = unkmthd
        self.symtab = symtab

        Construct a page macro expander.

        @param mainsym: Main symbol to be displayed.
        @type mainsym: str
        @param unkmthd: Resolution method of undefined symbols
        (C{PageMacro.KEEPMODE} or C{PageMacro.DELMODE}).
        @type unkmthd: int
        @param symtab: Symbol table.
        @type symtab: dict
        
recipes/Python/231512_Efficient_Comfortable_HTMLTemplate/recipe-231512.py