Use set method to save cos in find_similar instead of save cos directly

[quillcraftsman]

Is your feature request related to a problem? Please describe.
In the django package django-find-similar I use adapter from django model to TextToken in find-similar.
__init__ method works well. But I need to add new behavior the cos will be saved.

Describe the solution you'd like
Here we save cos directly.
text.cos = cos
create special method or setter to do in the TextToken class:

def set_cos(cos):
    self.cos = cos

Describe alternatives you've considered
we can create python @setter. But in this way we should make cos property protected and create @getter. It's not a problem, just need more attention and replacements.

Additional context