begin overloads
Declared in <bslstl_deque.h>
Return an iterator providing modifiable access to the first element in this deque, and the past-the-end iterator if this deque is empty.
Deque_Base<VALUE_TYPE>::iterator
begin() noexcept;Return a constant iterator to the first element in this deque.
Deque_Base<VALUE_TYPE>::const_iterator
begin() const noexcept;