Header[VOXEL_TO_WORLD] never used in Tck format

[jchoude]

If you use something similar to

hdr = tc.formats.header.get_header_from_anat(ref_filename)
out_tracts = tracts_format.create(output_filename, hdr)

where ref_filename is the name of the reference Nifti image, and you do NOT specify the reference anatomy in the create() call, an identity transform is applied when saving the streamlines.

Intuitively, we would expect the header created from the reference nifti to have some kind of effect.

I know that this is not currently actively developed, just wanted to flag it.

Workaround: always specify the anatFile param for the create call.