In PYTHON, Write a function using recursion called "merge_characters" that takes as a parameter a list that contains strings and/or nested lists of strings (i.e.["hello", ["sir", "john", ["is", "happy"]]]). This function should return a string that contains all of the characters from every string. Remember that this function must incorporate recursion.

Here's an example of what your function should return:

merge_characters(["hello", ["sir", "john", ["is", "happy"]]]) => "hellosirjohnishappy"