Multiple Inheritance
To specify a derived class when there is more than one
base class, we add each direct base class name as part of
the derived class' header. This is the same as with single
inheritance, except there is a comma separated list of
base classes.
class assets : public savings, public equity {.
  public:
    ...
};
The definition cannot be cyclical.
A direct base class.
     cannot be specified  more.
     than once for any derived class.