 Okay, this error is invalid call, non-existent function something in base something. This means that you're calling a function that doesn't exist in a class that you're trying to access. In this case, we're trying to get the length of people, which is a dictionary, but length is not a function inside the dictionary class, but length is a function in the string class. That means that if we change the variable that we're accessing, this will not give us any error, it will give us the result. And the same could be the other way around, if we want to check the size of the dictionary, but we're trying to access this string class, it will give us an error. In this case, size is for people. You can check the functions that are parts of a class by using the documentation and checking the name. For instance, now dictionary, we'll get here the dictionary, and here we can check the methods, which are functions inside of a class that are available to use there. So if you see this error anywhere, check that the variable that you're trying to access is the one that has the method or function that you're calling.