I changed EXAMPLE by EXAMPLES in degenerate_submanifold.py:

Author: Dicolevrai

src/sage/manifolds/differentiable/degenerate_submanifold.py

@@ -602,7 +602,7 @@ def _ambient_decomposition(self, screen=None):
          TM_{|\Sigma}=S(T\Sigma)\oplus_{orth}((Rad(T\Sigma)\oplus_{orth}(
             T\sigma^\perp\cap tr(TM))\oplus Rig(T\Sigma))
 
-        EXAMPLE:
+        EXAMPLES:
 
         A degenerate hyperplane the 4-dimensional Minkowski space `\RR^4_1`::