perf: lazily import our modules and external libraries (#624)

### Summary of Changes

We depend on several large libraries that take a while to load.
Previously, importing `Table` would already import almost all of them,
leading to horrendous startup times:

```
(Measure-Command { python -c "from safeds.data.tabular.containers import Table" }).TotalSeconds
```

➡️ 3.5068337 (seconds to import `Table` on main)

Now, we lazily import our own modules in the `__init__.py` files, and we
lazily import external libraries. The latter part is quite ugly, since
each function must now contain their external imports at the start.
There is no better solution, however, and the improvements are huge:

```
(Measure-Command { python -c "from safeds.data.tabular.containers import Table" }).TotalSeconds
```

➡️ 0.1683219 (seconds to import `Table` in this branch)

We still have to pay the cost for an import once we first import a
module, but at least this no longer has to happen fully upfront.

---------

Co-authored-by: megalinter-bot <[email protected]>

.github/linters/.ruff.toml

@@ -103,6 +103,10 @@ ignore = [
     "D106",
     "D107",
 ]
+"__init__.py" = [
+    # runtime-import-in-type-checking-block: Does not work with apipkg.
+    "TCH004",
+]
 
 [pydocstyle]
 convention = "numpy"

pyproject.toml

@@ -14,6 +14,7 @@ packages = [
 
 [tool.poetry.dependencies]
 python = "^3.11,<3.13"
+apipkg = "^3.0.2"
 ipython = "^8.8.0"
 levenshtein = ">=0.21.1,<0.26.0"
 matplotlib = "^3.6.3"
@@ -23,10 +24,10 @@ pillow = ">=9.5,<11.0"
 scikit-image = ">=0.21,<0.23"
 scikit-learn = "^1.2.0"
 seaborn = "^0.13.0"
+statsmodels = "^0.14.1"
 torch = {version = "^2.2.0", source = "torch_cuda121"}
 torchvision = {version = "^0.17.0", source = "torch_cuda121"}
 xxhash = "^3.4.1"
-statsmodels = "^0.14.1"
 
 [tool.poetry.group.dev.dependencies]
 pytest = ">=7.2.1,<9.0.0"

src/safeds/_config/__init__.py

@@ -1,6 +1,18 @@
 """Configuration for Safe-DS."""
 
-from ._device import _get_device
+from typing import TYPE_CHECKING
+
+import apipkg
+
+if TYPE_CHECKING:
+    from ._device import _get_device
+
+apipkg.initpkg(
+    __name__,
+    {
+        "_get_device": "._device:_get_device",
+    },
+)
 
 __all__ = [
     "_get_device",

src/safeds/_config/_device.py

@@ -1,6 +1,12 @@
-import torch
-from torch.types import Device
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from torch.types import Device
 
 
 def _get_device() -> Device:
+    import torch
+
     return torch.device("cuda") if torch.cuda.is_available() else torch.device("cpu")

src/safeds/_utils/__init__.py

@@ -1,6 +1,18 @@
 """Utilities for Safe-DS."""
 
-from ._hashing import _structural_hash
+from typing import TYPE_CHECKING
+
+import apipkg
+
+if TYPE_CHECKING:
+    from ._hashing import _structural_hash
+
+apipkg.initpkg(
+    __name__,
+    {
+        "_structural_hash": "._hashing:_structural_hash",
+    },
+)
 
 __all__ = [
     "_structural_hash",

src/safeds/_utils/_hashing.py

@@ -3,8 +3,6 @@
 import struct
 from typing import Any
 
-import xxhash
-
 
 def _structural_hash(*value: Any) -> int:
     """
@@ -20,6 +18,8 @@ def _structural_hash(*value: Any) -> int:
     hash
         Deterministic hash value
     """
+    import xxhash
+
     return xxhash.xxh3_64(_value_to_bytes(value)).intdigest()
 
 

src/safeds/data/image/containers/__init__.py

@@ -1,7 +1,20 @@
 """Classes that can store image data."""
 
-from ._image import Image
-from ._image_list import ImageList
+from typing import TYPE_CHECKING
+
+import apipkg
+
+if TYPE_CHECKING:
+    from ._image import Image
+    from ._image_list import ImageList
+
+apipkg.initpkg(
+    __name__,
+    {
+        "Image": "._image:Image",
+        "ImageList": "._image_list:ImageList",
+    },
+)
 
 __all__ = [
     "Image",

src/safeds/data/image/containers/_empty_image_list.py

@@ -4,6 +4,8 @@
 from typing import TYPE_CHECKING, Self
 
 from safeds._utils import _structural_hash
+from safeds.data.image.containers._image_list import ImageList
+from safeds.data.image.containers._single_size_image_list import _SingleSizeImageList
 from safeds.data.image.utils._image_transformation_error_and_warning_checks import (
     _check_add_noise_errors,
     _check_adjust_brightness_errors_and_warnings,
@@ -15,6 +17,7 @@
     _check_resize_errors,
     _check_sharpen_errors_and_warnings,
 )
+from safeds.exceptions import IndexOutOfBoundsError
 
 if TYPE_CHECKING:
     from pathlib import Path
@@ -23,10 +26,6 @@
 
     from safeds.data.image.containers import Image
 
-from safeds.data.image.containers._image_list import ImageList
-from safeds.data.image.containers._single_size_image_list import _SingleSizeImageList
-from safeds.exceptions import IndexOutOfBoundsError
-
 
 class _EmptyImageList(ImageList):
     """