def __call__(<EOL>self, expr,<EOL>safe=DEFAULT_SAFE, tostr=DEFAULT_TOSTR, scope=DEFAULT_SCOPE,<EOL>besteffort=DEFAULT_BESTEFFORT<EOL>):
raise NotImplementedError()<EOL>
Resolve input expression.

        :param str expr: configuration expression to resolve in this language.
        :param bool safe: safe run execution context (True by default).
        :param bool tostr: format the result.
        :param dict scope: execution scope (contains references to expression
            objects).
        :param bool besteffort: try to resolve unknown variable name from
            runtime context.