A developer cartridge, developing unit, and image forming apparatus are provided. The eyelid engaging means include armatures at distal ends, which engage eyelids of an end user and lift and hold up said eyelids in order to assist in installing andor removing contact lenses from the eyes of the end user. As a result, in various implementations the audio equalization filter may be more accurate than certain currently-available IIR equalization filters. Another step includes excavating the portion of the earth enclosed by the secant pile wall.