A zero-argument function that returns an object, conforming to the Iterator Protocol. In Javascript/Typescript in order to be iterable, an object must implement the "@@iterator" method
an iterator object.
Get the current column, or return undefined if the iterator was not yet started
Check if the iterator can return more columns
true if the iterator can return more columns, false if there are no columns left
Get the next column, or return undefined if the iterator's end was reached
Restart the iterator
The class DanMatrixColumnsIterator implements MatrixIterator interface and Iterable interface