add documentation for custom formatters

src/nominatim_api/__init__.py

@@ -39,5 +39,6 @@ from .results import (SourceTable as SourceTable,
                       SearchResult as SearchResult,
                       SearchResults as SearchResults)
 from .localization import (Locales as Locales)
+from .result_formatting import (FormatDispatcher as FormatDispatcher)
 
 from .version import NOMINATIM_API_VERSION as __version__

src/nominatim_api/result_formatting.py

@@ -20,8 +20,8 @@ ErrorFormatFunc = Callable[[str, str, int], str]
 
 
 class FormatDispatcher:
-    """ Helper class to conveniently create formatting functions in
-        a module using decorators.
+    """ Container for formatting functions for results.
+        Functions can conveniently be added by using decorated functions.
     """
 
     def __init__(self, content_types: Optional[Mapping[str, str]] = None) -> None: