/usr/share/mime-info/dia.keys is in dia-common 0.97.3+git20160930-8.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 | application/x-dia-diagram:
open=dia %f
view=dia %f
icon-filename=${prefix}/share/icons/hicolor/48x48/apps/dia.png
|