PEP 690: Add a simple example of the behavior (#2577)

pep-0690.rst

@@ -140,6 +140,41 @@ Dynamic imports using ``__import__()`` or ``importlib.import_module()`` are
 also never lazy.
 
 
+Example
+-------
+
+Say we have a module ``spam.py``::
+
+    # simulate some work
+    import time
+    time.sleep(10)
+    print("spam loaded")
+
+And a module ``eggs.py`` which imports it::
+
+    import spam
+    print("imports done")
+
+If we run ``python -L eggs.py``, the ``spam`` module will never be imported
+(because it is never referenced after the import), ``"spam loaded"`` will never
+be printed, and there will be no 10 second delay.
+
+But if ``eggs.py`` simply references the name ``spam`` after importing it, that
+will be enough to trigger the import of ``spam.py``::
+
+    import spam
+    print("imports done")
+    spam
+
+Now if we run ``python eggs.py``, we will see the output ``"imports done"``
+printed first, then a 10 second delay, and then ``"spam loaded"`` printed after
+that.
+
+Of course, in real use cases (especially with lazy imports), it's not
+recommended to rely on import side effects like this to trigger real work. This
+example is just to clarify the behavior of lazy imports.
+
+
 Debuggability
 -------------