local function __TS__StringSubstr(self, from, length)
    if from ~= from then
        from = 0
    end
    if length ~= nil then
        if length ~= length or length <= 0 then
            return ""
        end
        length = length + from
    end
    if from >= 0 then
        from = from + 1
    end
    return string.sub(self, from, length)
end