"Mixin is not defined" error when trying to use template mixins

[solidstate1991 via Digitalmars-d-learn]

There's a template mixin in my dimage project's new version in 
base.d, and when I try to access it from another file I get two 
errors:

undefined identifier `ChunkyAccess4bit`, did you mean template 
`ChunkyAccess4Bit()`?

and

mixin `dimage.tga.TGA.ChunkyAccess4bit!()` is not defined

Should I put the template into the base class of TGA (Image) 
instead of keeping it outside of that?