Restructure sub-modules

See #37 (closed) for details.

Sub-modules

The following sub-modules remain:

• hotopy.holo (former hotopy.phase merged with hotopy.propagation)
• hotopy.tomo (merge of hotopy.tomo and hotopy.astra)
• hotopy.image
• hotopy.datasets
• hotopy.utils (merge of hotopy.fourier, hotopy.xray, hotopy.utils, hotopy.io)

Sub-modules support top-level imports

(Most) Sub-modules allow convenient imports from their respective top-level, e.g. from hotopy.image import GaussianBlur, from hotopy.holo import simulate_hologram etc.

Closes #37 (closed).

hotopy/datasets/__init__.py

 """
-==================================================
+=========================================
 Example datasets (:mod:`hotopy.datasets`)
-==================================================
+=========================================
 
-Experimental holographic datasets (:mod:`.holograms`)
------------------------------------------------------
+Experimental holographic datasets
+---------------------------------
 .. autosummary::
     :toctree: generated/
 
-    holograms.beads
-    holograms.radiodurans
-    holograms.macrophage
-    holograms.world
+    beads
+    radiodurans
+    macrophage
+    world_holograms
 
 Example:
 
-    >>> from hotopy.datasets.holograms import beads
+    >>> from hotopy.datasets import beads
     >>> data = beads()
     >>> # list content
     >>> print(list(data.keys()))   # ['holograms', 'fresnelNumbers']
@@ -27,7 +27,7 @@ Example:
 
     This datasets can be used for phase retrieval, e.g. with CTF or Tikhonov.
 
-    >>> from hotopy.phase import Tikhonov
+    >>> from hotopy.holo import Tikhonov
     >>> imshape = holos.shape[-2:]
     >>> alpha = [0, 5e-2]
     >>> betadelta = 0.01  # 1% effective absorption
@@ -36,18 +36,27 @@ Example:
     >>> rec_tik = tik(holos).cpu().numpy()
 
 
-Simulation phantoms (:mod:`.phantoms`)
---------------------------------------
+Simulation phantoms
+-------------------
 .. autosummary::
     :toctree: generated/
 
-    phantoms.dicty
-    phantoms.dicty_multi
-    phantoms.world
+    dicty
+    dicty_multi
+    world
 
 .. author: Jens Lucht, 2023-2024
 """
 
-from ._fetcher import _DataFetcher
-
-fetcher = _DataFetcher()
+from ._holograms import beads, radiodurans, macrophage, world_holograms
+from ._phantoms import dicty, dicty_multi, world
+
+__all__ = [
+    "beads",
+    "radiodurans",
+    "macrophage",
+    "world_holograms",
+    "dicty",
+    "dicty_multi",
+    "world",
+]