fix: warning and add an exception if using class alone (#3552)

* fix: warning and add an exception if using class alone

* chore: adding changelog file 3552.fixed.md [dependabot-skip]

* ci: auto fixes from pre-commit.com hooks.

for more information, see https://pre-commit.ci

* feat: clarifying warning

---------

Co-authored-by: pyansys-ci-bot <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: 3 people

doc/changelog.d/3552.fixed.md

@@ -0,0 +1 @@
+fix: warning and add an exception if using class alone

src/ansys/mapdl/core/mapdl.py

@@ -27,7 +27,7 @@ class MapdlBase(_MapdlExtended):
     """Base MAPDL class shared across all MAPDL subclasses.
 
     .. warning:: This class should NOT be imported by itself.
-       You should always import a subclass of it
-    """
+       You should always import a subclass of it like
+       :class:`MapdlGrpc <ansys.mapdl.core.mapdl_grpc.MapdlGrpc>`
 
-    pass
+    """