They just rate it center. There is no single media source that will never have any bias at all. So that would mean there would never be an center.

>AP is a source that AllSides has struggled to rate, due to its content seeming to toe the line between Center and Lean Left. People on the right may be more likely to see AP’s content as clearly Lean Left. While AP's news and world reporting is largely Center, AllSides has found AP often includes subjective, leftward analysis in hard news reports and omits sources in its political writing; in addition, its fact checks are biased to the left