Filterable() doesn't work

I tried to use the Filterable() function in my grid to filter by multiple checkboxes, but I can't.

Following this example Grid / Filter Multi Checkboxes, when I add the function Filterable() to my column bound it doesn't appear the function Multi(). The available functions are Enabled(), Equals(), Extra(), GetHashCode(), GetType(), Messages(), Operators(), ToString() and UI().

Moreover, I want to filter first the rows with value "X" and after the rest of the rows ("Y" and "Z")​.

I'll appreciate any help.