Python 3.5.2 (default, Nov 17 2016, 17:05:23) 
[GCC 5.4.0 20160609] on linux
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(InteractiveConsole)
>>> from maasserver.bootsources import BootSourceCache
>>> BootSourceCache.objects.filter(arch='amd64', subarch='generic')
[<BootSourceCache: <BootSourceCache os=ubuntu, release=trusty, arch=amd64, subarch=generic, kflavor=lowlatency>>, <BootSourceCache: <BootSourceCache os=ubuntu, release=yakkety, arch=amd64, subarch=generic, kflavor=lowlatency>>, <BootSourceCache: <BootSourceCache os=ubuntu, release=yakkety, arch=amd64, subarch=generic, kflavor=generic>>, <BootSourceCache: <BootSourceCache os=ubuntu, release=xenial, arch=amd64, subarch=generic, kflavor=generic>>, <BootSourceCache: <BootSourceCache os=centos, release=centos70, arch=amd64, subarch=generic, kflavor=generic>>, <BootSourceCache: <BootSourceCache os=ubuntu, release=precise, arch=amd64, subarch=generic, kflavor=generic>>, <BootSourceCache: <BootSourceCache os=centos, release=centos66, arch=amd64, subarch=generic, kflavor=generic>>, <BootSourceCache: <BootSourceCache os=ubuntu, release=xenial, arch=amd64, subarch=generic, kflavor=lowlatency>>, <BootSourceCache: <BootSourceCache os=ubuntu, release=zesty, arch=amd64, subarch=generic, kflavor=generic>>, <BootSourceCache: <BootSourceCache os=ubuntu, release=trusty, arch=amd64, subarch=generic, kflavor=generic>>, <BootSourceCache: <BootSourceCache os=grub-efi-signed, release=uefi, arch=amd64, subarch=generic, kflavor=bootloader>>, <BootSourceCache: <BootSourceCache os=ubuntu, release=zesty, arch=amd64, subarch=generic, kflavor=lowlatency>>]