Hello Vlad,
so you don't use SEGW for creating GW Services?
I'm not using SE80 GW Data Model but SEGW.
So my description may depend on that.
Usually, the method get_entityset is inherited from interface /IWBEP/IF_MGW_APPL_SRV_RUNTIME and can be found in a class interface /IWBEP/CL_MGW_PUSH_ABS_DATA.
Your class (Z..*_DPC) is inheriting from /IWBEP/CL_MGW_PUSH_ABS_DATA.
You should find your class by opening the /IWBEP/CL_MGW_PUSH_ABS_DATA and go there for
subclasses. Once there your are looking for variable et_entityset .
Kind regards,
Alex