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A configuration file can be extended (i.e. included) by other files. For this,
-a ``DEFAULT`` section must contain an ``extends`` key which value points to one
+a ``DEFAULT`` section must contain an ``extends`` key whose value points to one
or more files which will be merged into the current files by adding new sections
and fields. If a file loaded by ``extends`` contains sections or keys that
already exist in the original file, they will not override the previous values.