def make_great(magicians_list[:]):Don't use [:] on the parameter
Use [:] inside the function
def make_great(magicians_list): list_aux = [] for magician in magicians_list[:]: ... ...
If you actually want to pass in a copy of the list and the function uses the passed-in list, use
magicians_aux = make_great(magicians[:]) def make_great(magicians_list): list_aux = [] for magician in magicians_list: ... ...