Get the Features on which the Fillet Feature is creating?

Hi, everyone.

I'm processing the Fillet Features, cause common Fillet Feature is creating on some edges, which are from previous Features. So, given a selected Fillet Feature, I wanna get the previous features related to the edges. However, I find the ISimpleFilletData has a function called Features, but as below, the Fillet is based on the Extrusion Feature, but when I call .Feature function, the returned valued is 0 or null. So, can someone help explain the use of this Features function, and what should I do to get my target?