Inheriting from a COM Implementation class

I have a COM interface in the .idl file that looks like this:
import "oaidl.idl";
import "ocidl.idl";
import "myBase.idl";
     [
          object,
          uuid(E655B3C6-05EC-4A1B-B08F-488826F25234),
     
          helpstring("ISymbol Interface"),
          pointer_default(unique)
     ]
     interface IDerivedSymbol : IBaseSymbol
     {
      //added 2 additional methods here    

     };

[
     uuid(A66139F8-A5FE-4CC0-AE92-ECEB0019B263),
     version(1.0),
     helpstring("1.0 Type Library")
]
library SYMBOLLib
{
     importlib("stdole32.tlb");
     importlib("stdole2.tlb");
     [
          uuid(C2827C0A-16E4-4364-854A-179BE3D33A88),
          helpstring("Symbol Class")
     ]
     coclass DerivedSymbol
     {
          [default] interface IDerivedSymbol;
               
        }
};
My implementaion class of the IDerivedSymbol interface is called CDerivedSymbol
How do I inherit the implementation class of the IBaseSymbol interface,(CBaseSymbol) so I can just reuse the existing methods in that interface.

Thanks