Yes, it gets a trailing comma if it's on it's own line. That way when you add/remove arguments in a multi-line call it's only a one-line diff. This doesn't apply when the diff is only one line anyway.
Who's to say you don't add a new argument to the function in the future, like
my_print(
"This string has two parameters, `a` which is equal to {a} and `b` which is equal to {b}",
a=1,
b=2,
color_negative_red=True,
)