feature/import-any-reader-from-readers (AllenCellModeling#326)

* allow reader import

* use forward ref

* fix docs

aicsimageio/readers/__init__.py

@@ -1,6 +1,38 @@
 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
 
-from .array_like_reader import ArrayLikeReader  # noqa: F401
-from .ome_tiff_reader import OmeTiffReader  # noqa: F401
-from .tiff_reader import TiffReader  # noqa: F401
+from typing import TYPE_CHECKING, Type
+
+# To add a new reader add it both to TYPE_CHECKING and _READERS
+
+if TYPE_CHECKING:
+    from .array_like_reader import ArrayLikeReader  # noqa: F401
+    from .bioformats_reader import BioformatsReader  # noqa: F401
+    from .czi_reader import CziReader  # noqa: F401
+    from .lif_reader import LifReader  # noqa: F401
+    from .ome_tiff_reader import OmeTiffReader  # noqa: F401
+    from .reader import Reader
+    from .tiff_reader import TiffReader  # noqa: F401
+
+
+# add ".relativepath.ClassName"
+_READERS = (
+    ".array_like_reader.ArrayLikeReader",
+    ".bioformats_reader.BioformatsReader",
+    ".czi_reader.CziReader",
+    ".lif_reader.LifReader",
+    ".ome_tiff_reader.OmeTiffReader",
+    ".tiff_reader.TiffReader",
+)
+_LOOKUP = {k.rsplit(".", 1)[-1]: k for k in _READERS}
+__all__ = list(_LOOKUP)
+
+
+def __getattr__(name: str) -> Type["Reader"]:
+    if name in _LOOKUP:
+        from importlib import import_module
+
+        path, clsname = _LOOKUP[name].rsplit(".", 1)
+        mod = import_module(path, __name__)
+        return getattr(mod, clsname)
+    raise AttributeError(f"module {__name__!r} has no attribute import name {name!r}")