skip triangle requirement on arm64

Dockerfile

@@ -117,6 +117,12 @@ RUN --mount=type=cache,target=/root/.cache/pip cat pytorch-requirements.txt | so
 COPY ./rastervision_aws_batch/requirements.txt /opt/src/batch-requirements.txt
 COPY ./rastervision_aws_s3/requirements.txt /opt/src/s3-requirements.txt
 COPY ./rastervision_core/requirements.txt /opt/src/core-requirements.txt
+
+# Pip wheels for triangle are missing for ARM64 architectures and building
+# from source fails, so we skip it.
+RUN if [ "${TARGETARCH}" = "arm64" ]; \
+    then sed -i '/^triangle.*$/d' /opt/src/core-requirements.txt; fi
+
 COPY ./rastervision_gdal_vsi/requirements.txt /opt/src/gdal-requirements.txt
 COPY ./rastervision_pipeline/requirements.txt /opt/src/pipeline-requirements.txt
 COPY ./rastervision_aws_sagemaker/requirements.txt /opt/src/sagemaker-requirements.txt

rastervision_core/rastervision/core/data/utils/aoi_sampler.py

@@ -3,7 +3,6 @@
 import numpy as np
 from shapely.geometry import Polygon, MultiPolygon, LinearRing
 from shapely.ops import unary_union
-from triangle import triangulate
 
 
 class AoiSampler():
@@ -67,6 +66,8 @@ def triangulate_polygon(self, polygon: Polygon) -> dict:
         """Extract vertices and edges from the polygon (and its holes, if any)
         and pass them to the Triangle library for triangulation.
         """
+        from triangle import triangulate
+
         vertices, edges = self.polygon_to_graph(polygon)
 
         holes = polygon.interiors

rastervision_pytorch_learner/rastervision/pytorch_learner/dataset/dataset.py

@@ -385,7 +385,11 @@ def __init__(self,
                 p.intersection(extent_polygon) for p in self.aoi_polygons
             ]
             if efficient_aoi_sampling:
-                self.aoi_sampler = AoiSampler(self.aoi_polygons)
+                try:
+                    self.aoi_sampler = AoiSampler(self.aoi_polygons)
+                except ModuleNotFoundError:
+                    log.info('Ignoring efficient_aoi_sampling since triangle '
+                             'is not installed.')
 
     def get_resize_transform(
             self, transform: Optional[A.BasicTransform],