Expose measure_obs like make_palette: re-export from pl/__init__

Follow the established public-helper pattern (make_palette is defined under pl/
and re-exported in pl/__init__) rather than inventing a top-level
spatialdata_plot.utils module. Public form: `from spatialdata_plot.pl import measure_obs`.

Author: timtreis

src/spatialdata_plot/pl/__init__.py

@@ -1,8 +1,10 @@
 from ._palette import make_palette, make_palette_from_data
 from .basic import PlotAccessor
+from .utils import measure_obs
 
 __all__ = [
     "PlotAccessor",
     "make_palette",
     "make_palette_from_data",
+    "measure_obs",
 ]

tests/pl/test_utils.py

@@ -12,12 +12,12 @@
 from spatialdata.models import PointsModel, ShapesModel, TableModel
 
 import spatialdata_plot
+from spatialdata_plot.pl import measure_obs
 from spatialdata_plot.pl.render_params import Color, ColorLike
 from spatialdata_plot.pl.utils import (
     _apply_cmap_alpha_to_datashader_result,
     _datashader_map_aggregate_to_color,
     _set_outline,
-    measure_obs,
     set_zero_in_cmap_to_transparent,
 )
 from tests.conftest import DPI, PlotTester, PlotTesterMeta