bsl::unordered_set<Attribute, AttributeHash>::insert

Insert into this set the value of each value_type object in the range starting at the specified first iterator and ending immediately before the specified last iterator, if a key equivalent to the object is not already contained in this set. The (template parameter) type INPUT_ITERATOR shall meet the requirements of an input iterator defined in the C++11 standard [24.2.3]providing access to values of a type convertible to value_type, and value_type must be emplace‐constructible from *i into this set, where i is a dereferenceable iterator in the range [first .. last)] (see {Requirements on KEY}). The behavior is undefined unless first and last refer to a sequence of valid values where first is at a position at or before last.