#include <vector>
#include <algorithm>
 
class Foo;
 
class BaseA {
protected:
    bool hasChild() const { return !childs_.empty(); }
    std::vector<Foo> childs_;
};
 
class BaseB {
protected:
    bool hasChild() const { return false; }
};
 
class Foo : public BaseA, public BaseB {
public:
  bool hasGrandChild() const {
    return std::any_of(childs_.begin(), childs_.end(), [](Foo const &foo) {
        return foo.BaseA::hasChild();
      });
  }  
};
 
int main()
{
  Foo foo;
  foo.hasGrandChild();
  return 0;
}

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