AlertDialog.dismiss()?

AlertDialog.dismiss()?

I am new in android and I am learning from developer.android.com site.
Then I came across to AlertDialog.dismiss() where in site it is written
that
This method Dismiss this dialog nad remove it from the screen. This method
can be invoked safely from any thread. Note that you should not override
this method to do cleanup when the dialog is dismissed, instead implement
that in onStop().
But I did not understand the mean of this line-
Note that you should not override this method to do cleanup when the
dialog is dismissed, instead implement that in onStop()
what is the mean of above line?
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