Added get and keys methods to AttrTree
Added get and keys methods to AttrTree

vascotenner/holoviews,mjabri/holoviews,mjabri/holoviews,basnijholt/holoviews,ioam/holoviews,mjabri/holoviews,vascotenner/holoviews,basnijholt/holoviews,basnijholt/holoviews,ioam/holoviews,ioam/holoviews,vascotenner/holoviews