+ def _rewrite(me, op, rec):
+ """
+ Rewrite the file, according to OP.
+
+ The OP may be one of the following.
+
+ `create' There must not be a record matching REC; add a new
+ one.
+
+ `remove' There must be a record matching REC: remove it.
+
+ `update' There must be a record matching REC: write REC in its
+ place.
+ """