OOPS: how to enforce that a function is implemented in derived class

SystemVerilog
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2

In reply to verif_learner:

This is known as an abstract class with pure virtual methods

virtual class base;
  pure virtual function void func_x;
  virtual function void func_y;
    func_x;
  endfunction
endclass

class base cannot be constructed directly; it must be extended with an implementation of func_x.