[WIP] feat(aliby): base image class lazy-loads dummy image

WHY IS THIS CHANGE NEEDED?:
- need function that creates the expected output from dummy image file,
  as an interface for other classes' get_data_lazy() methods

HOW DOES THE CHANGE SOLVE THE PROBLEM?:
- create abstract method that loads the dummy image file and returns
  2d dask array
- define function to get examples directory, following logfile_parser.legacy

WHAT SIDE EFFECTS DOES THIS CHANGE HAVE?:
- only able to handle one TIF file (i.e. 1 z-section)

EVIDENCE THAT COMMIT WORKS:
- created a test class that extends BaseLocalImage and has a
  get_data_lazy() function that extends the base class's function; it is
  able to load the dummy image into a dask array

REFERENCES:
- issue #53

src/aliby/io/image.py

 #!/usr/bin/env python3
 
 import typing as t
-from abc import ABC, abstractproperty
+from abc import ABC, abstractmethod, abstractproperty
 from datetime import datetime
+from importlib_resources import files
 from pathlib import Path, PosixPath
 
 import dask.array as da
@@ -13,6 +14,11 @@ from tifffile import TiffFile
 from agora.io.metadata import dir_to_meta
 
 
+def get_examples_dir():
+    """Get examples directory which stores dummy image for tiler"""
+    return files("aliby").parent.parent / "examples" / "tiler"
+
+
 def get_image_class(source: t.Union[str, int, t.Dict[str, str], PosixPath]):
     """
     Wrapper to pick the appropiate Image class depending on the source of data.
@@ -68,6 +74,21 @@ class BaseLocalImage(ABC):
         )
         return self._rechunked_img
 
+    @abstractmethod
+    def get_data_lazy(self) -> da.Array:
+        """Return 5D dask array. For lazy-loading multidimensional tiff files. Dummy image."""
+        examples_dir = get_examples_dir()
+        # TODO: Make this robust to having multiple TIFF images, one for each z-section,
+        # all falling under the same "pypipeline_unit_test_00_000001_Brightfield_*.tif"
+        # naming scheme.  The aim is to create a multidimensional dask array that stores
+        # the z-stacks.
+        img_filename = "pypipeline_unit_test_00_000001_Brightfield_003.tif"
+        img_path = examples_dir / img_filename
+        # img has two dimensions: x, y
+        # This line assumes that the image being imported is of shape (1, *, *).
+        img = imread(str(img_path))[0]
+        return img
+
     @abstractproperty
     def name(self):
         pass