__next__ and StopIteration

[Charles Hixson]

I'm trying to write a correct iteration over a doubly indexed container, 
and what I've got so far is:    def __next__ (self):
         for row    in    range(self._rows):
             for col in range(self._cols):
                 if self._grid[row][col]:
                     yield    self._grid[row][col]
                 #end    if
             #end    for col
         #end    for row
         raise    StopIteration

What bothers me is that it doesn't look like it would continue to raise 
StopIteration if it were called again, which is what 
https://docs.python.org/3/library/stdtypes.html#iterator.__next__ says 
is correct.  How should this be fixed?