Address reviewer comments: use class name dynamically, jupyter-execute block, improve phrasing

Author: sshekhar563

doc/internals/how-to-create-custom-index.rst

@@ -138,17 +138,20 @@ just the class name. You can customize this by implementing the
 string representation of the index.
 
 The ``_repr_inline_`` method receives a ``max_width`` argument (number of
-characters) that can be used to truncate the output if needed:
+characters) that indicates the available space for the representation. If the
+representation exceeds this width, it should be truncated:
 
-.. code-block:: python
+.. jupyter-execute::
+
+    from xarray import Index
 
     class MyIndex(Index):
         def __init__(self, data):
             self._data = data
 
         def _repr_inline_(self, max_width: int) -> str:
             # Return a concise representation
-            return f"MyIndex (size={len(self._data)})"
+            return f"{self.__class__.__name__} (size={len(self._data)})"
 
 Here are some examples from Xarray's built-in indexes:
 
@@ -237,7 +240,7 @@ regularly spaced 2-dimensional data) that internally relies on two
 
         def _repr_inline_(self, max_width: int) -> str:
             dims = [idx.dim for idx in self._xy_indexes.values()]
-            return f"RasterIndex (dims={dims})"
+            return f"{self.__class__.__name__} (dims={dims})"
 
 
 This basic index only supports label-based selection. Providing a full-featured