Omissions in `xray.astra` docs

[bwohlberg]

There are some minor omissions in the xray.astra docs:

Missing Returns: sections for _project_coords:

scico/scico/linop/xray/astra.py

Lines 64 to 76 in a0e99bd

	def _project_coords(
	x_volume: np.ndarray, vol_geom: VolumeGeometry, proj_geom: ProjectionGeometry
	) -> np.ndarray:
	"""
	Transform volume (logical) coordinates into world coordinates based
	on ASTRA geometry objects.
	Args:
	x_volume: (..., 3) vector(s) of volume (AKA logical) coordinates
	vol_geom: ASTRA volume geometry object.
	proj_geom: ASTRA projection geometry object.
	"""
	det_shape = (proj_geom["DetectorRowCount"], proj_geom["DetectorColCount"])

and for XRayTransform2D.fbp:

scico/scico/linop/xray/astra.py

Lines 309 to 320 in a0e99bd

	def fbp(self, sino: jax.Array, filter_type: str = "Ram-Lak") -> jax.Array:
	"""Filtered back projection (FBP) reconstruction.
	Perform tomographic reconstruction using the filtered back
	projection (FBP) algorithm.
	Args:
	sino: Sinogram to reconstruct.
	filter_type: Select the filter to use. For a list of options
	see `cfg.FilterType` in the `ASTRA documentation
	<https://www.astra-toolbox.com/docs/algs/FBP_CUDA.html>`__.
	"""

Clarification needed on presence of angles and vectors at

scico/scico/linop/xray/astra.py

Lines 453 to 454 in a0e99bd

	angles: Array of projection angles in radians.
	vectors: Array of geometry specification vectors.

and similar clarification could be provided in docs for XRayTransform3D.__init__.

Typo in line

scico/scico/linop/xray/astra.py

Line 436 in a0e99bd

"""Convert ASTRA geometry specificiation to a SCICO projection matrix.

Use of "parallel3d_vec" format appears to be incompatible with angles option referred to above:

scico/scico/linop/xray/astra.py

Line 439 in a0e99bd

projection matrix, assuming "parallel3d_vec" format.

It would also be worth adding some discussion of the meaning of "world coordinates" referred to in functions such as project_world_coordinates.

[bwohlberg]

Resolved by #578.