give doctests that f_vector for unbounded polyhedra works now

src/sage/geometry/polyhedron/base.py

@@ -5336,15 +5336,32 @@ def f_vector(self):
 
         OUTPUT:
 
-        Returns a vector whose ``i``-th entry is the number of
-        ``i``-dimensional faces of the polytope.
+        Returns a vector whose `i`-th entry is the number of
+        `i-2`-dimensional faces of the polytope.
+
+        Note that the ``vertices`` as given by :meth:`Polyhedron_base.vertices`
+        do not need to correspond to `0`-dimensional faces. If a polyhedron
+        contains `k` lines they correspond to `k`-dimensional faces.
 
         EXAMPLES::
 
             sage: p = Polyhedron(vertices=[[1, 2, 3], [1, 3, 2],
             ....:     [2, 1, 3], [2, 3, 1], [3, 1, 2], [3, 2, 1], [0, 0, 0]])
             sage: p.f_vector()
             (1, 7, 12, 7, 1)
+
+            sage: polytopes.cyclic_polytope(4,10).f_vector()
+            (1, 10, 45, 70, 35, 1)
+
+            sage: polytopes.hypercube(5).f_vector()
+            (1, 32, 80, 80, 40, 10, 1)
+
+        Polyhedra with lines do not have `0`-faces::
+
+            sage: Polyhedron(ieqs=[[1,-1,0],[1,1,0]]).f_vector()
+            (1, 0, 2, 1)
+            sage: Polyhedron(ieqs=[[1,-1,0,0],[1,1,0,0]]).f_vector()
+            (1, 0, 0, 2, 1)
         """
         return self.combinatorial_polyhedron().f_vector()
 

src/sage/geometry/polyhedron/parent.py

@@ -629,7 +629,7 @@ def change_ring(self, base_ring, backend=None, ambient_dim=None):
 
     def _coerce_base_ring(self, other):
         r"""
-        Return the common base rincg for both ``self`` and ``other``.
+        Return the common base ring for both ``self`` and ``other``.
 
         This method is not part of the coercion framework, but only a
         convenience function for :class:`Polyhedra_base`.