size_type size() const noexcept { return skeletons.size(); }
reference operator[](size_type i) noexcept { return *skeletons[i]; }
const_reference operator[](size_type i) const noexcept { return *skeletons[i]; }
size_type size() const noexcept { return skeletons.size(); }
reference operator[](size_type i) noexcept { return *skeletons[i]; }
const_reference operator[](size_type i) const noexcept { return *skeletons[i]; }