Functions Acting on a List

I have a function that operates on a string list input. I noticed that the script fails in the case of attempting to convert a string to a list inside the function request:

my_app.MY_FUNCTION(string_item.toList())

my_app.MY_FUNCTION({string_item})

To get this to work, I had to convert the string to a list outside the function:

my_list = string_item.toList()

my_app.MY_FUNCTION(my_list)

John M. Whitney