An index signature parameter type cannot be a literal type or generic type. Consider using a mapped object type instead.

Index signatures in C# and .NET, like those used in IronPython with generic types, require dynamic or type-agnostic types as index values. Literal types such as `int` or `List<int>` cannot be directly used as indexes because they are specific and static. Instead, you should use a mapped object type, like `object` or an instance of a generic type that accepts any type.

For example, if you want to index into a `List<T>` with a generic type parameter `T`, you would typically use an `object` or another collection that can hold instances of `T`[^1]:

public void IndexWithGeneric(List<object> listToIndex, Type elementType) {
    var targetIndex = ... // A value of type `T` that you want to use as an index.
    int indexValue = Convert.ToInt32(targetIndex); // If targetIndex is not already an int

    // Now you can access the element at that index, assuming it's compatible:
    var item = listToIndex[indexValue];
}

Similarly, in IronPython, you might use a dictionary with `str` keys and a `Dictionary[object, T]` to allow any value type:

from System.Collections.Generic import Dictionary

def index_with_generic(d: Dictionary[str, Dictionary[object, T]], key_type: Type[T]) -> T:
    target_key = ...  # An instance of key_type
    target_index = target_key  # Assuming key_type is hashable, it can act as an index
    return d[target_index]