add graph layer (#292)

Hi.

This PR adds "graph" to the list of existing layers.
It's required by PR napari/napari#5861 which adds a new napari graph
layer.

---------

Co-authored-by: Jonas Windhager <jonas.windhager@uzh.ch>
Co-authored-by: Talley Lambert <talley.lambert@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Nathan Clack <nclack@chanzuckerberg.com>
Co-authored-by: Nathan Clack <nclack@gmail.com>
Co-authored-by: Jonas Windhager <jonas@windhager.io>

_docs/templates/_npe2_writers_guide.md.jinja

@@ -58,7 +58,7 @@ by the corresponding writer contribution in the manifest).
    ```python
    DataType = Any  # usually something like a numpy array, but varies by layer
    LayerAttributes = dict
-   LayerName = Literal["image", "labels", "points", "shapes", "surface", "tracks", "vectors"]
+   LayerName = Literal["graph", "image", "labels", "points", "shapes", "surface", "tracks", "vectors"]
    FullLayerData = Tuple[DataType, LayerAttributes, LayerName]
    MultiWriterFunction = Callable[[str, List[FullLayerData]], List[str]]
    ```

src/npe2/_inspection/_visitors.py

@@ -235,6 +235,9 @@ def napari_get_writer(self, node: ast.FunctionDef):
         # we can't convert this to an npe2 command contribution
         pass  # pragma: no cover
 
+    def napari_write_graph(self, node: ast.FunctionDef):
+        self._parse_writer(node, "graph")  # pragma: no cover
+
     def napari_write_image(self, node: ast.FunctionDef):
         self._parse_writer(node, "image")
 

src/npe2/manifest/contributions/_writers.py

@@ -7,6 +7,7 @@
 
 
 class LayerType(str, Enum):
+    graph = "graph"
     image = "image"
     labels = "labels"
     points = "points"

src/npe2/types.py

@@ -46,7 +46,7 @@ def __array__(self) -> "np.ndarray":
 
 
 LayerName = Literal[
-    "image", "labels", "points", "shapes", "surface", "tracks", "vectors"
+    "graph", "image", "labels", "points", "shapes", "surface", "tracks", "vectors"
 ]
 Metadata = Dict
 DataType = Union[ArrayLike, Sequence[ArrayLike]]

tests/conftest.py

@@ -118,6 +118,7 @@ class HookSpecs:
         def napari_provide_sample_data(): ...  # type: ignore
         def napari_get_reader(path): ...
         def napari_get_writer(path, layer_types): ...
+        def napari_write_graph(path, data, meta): ...
         def napari_write_image(path, data, meta): ...
         def napari_write_labels(path, data, meta): ...
         def napari_write_points(path, data, meta): ...