Implement find_distributions for _BackendPathFinder

Author: abravalheri

src/pyproject_hooks/_in_process/_in_process.py

@@ -106,6 +106,13 @@ def find_spec(self, fullname, _path, _target=None):
 
         return spec
 
+    def find_distributions(self, context=None):
+        # Delayed import: Python 3.7 does not contain importlib.metadata
+        from importlib.metadata import DistributionFinder, MetadataPathFinder
+
+        context = DistributionFinder.Context(path=self.backend_path)
+        return MetadataPathFinder.find_distributions(context=context)
+
 
 def _supported_features():
     """Return the list of options features supported by the backend.