Return a reference providing non-modifiable access to the mapped-value associated with a key that is equivalent to the specified key, if such an entry exists; otherwise, throw a std::out_of_range exception. Note that this method may also throw a different kind of exception if the (user-supplied) comparator throws.
Declared in <bslstl_map.h>
add_lvalue_reference<pair<shared_ptr<Statistics>, shared_ptr<Collector<OsLinux>>> const>::type
at(key_type const& key) const;