Added __iter__ function to OBIView lines

python/obitools3/obidms/_obidms.pyx

@@ -637,6 +637,10 @@ cdef class OBIView_line :
 
         (((self.view).columns)[column_name]).set_line(self.index, value)
 
+    def __iter__(self):
+        for column_name in ((self.view).columns) :
+            yield column_name
+
     def __contains__(self, str column_name):
         return (column_name in self.view.columns)