Missing the tetrahedron group (tetraOnR3 in escnn.gspaces?)

[chAwater]

Hi,

I'm trying to build 3D equivariant CNN and I found the tetrahedron symmetry group ("Describes 3D rotation symmetries of a tetrahedron in the space R3") is missing in action-on-volume.

Is there any way to build it (by subgroup or isomorphism)? Thanks!

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escnn/docs/source/api/escnn.gspaces.rst

Lines 43 to 44 in 0e8d301

	Indeed, in 3D, the only discrete 3D rotational symmetry groups are the symmetries of the few platonic solids (the
	tetrahedron group, the octahedron group and the icosahedron group).

escnn/docs/source/api/escnn.gspaces.rst

Lines 50 to 51 in 0e8d301

	Conversely, since there are only a few options in 3D, we provide a different method for each of them
	(e.g. :func:`~escnn.gspaces.icoOnR3` or :func:`~escnn.gspaces.octaOnR3`).

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BTW, I tried

from escnn.gspaces import GSpace3D
GSpace3D((False, 'tetra'))

but got

escnn/escnn/group/groups/o3group.py

Lines 644 to 648 in 0e8d301

	elif so3_sg_id[0] == 'tetra':
	# sg = escnn.group.tetra_group()
	# parent_mapping = so3_to_o3(adj, sg)
	# child_mapping = o3_to_so3(adj, sg)
	raise NotImplementedError()