do not rule out singleton axis as easily

(we cannot fail to load arrays with singleton axes
because of trying to be strict)

Author: FynnBe

bioimageio/core/axis.py

@@ -71,7 +71,7 @@ def create(cls, axis: AxisLike) -> Axis:
 
 @dataclass
 class AxisInfo(Axis):
-    maybe_singleton: bool
+    maybe_singleton: bool  # TODO: replace 'maybe_singleton' with size min/max for better axis guessing
 
     @classmethod
     def create(cls, axis: AxisLike, maybe_singleton: Optional[bool] = None) -> AxisInfo:
@@ -81,17 +81,17 @@ def create(cls, axis: AxisLike, maybe_singleton: Optional[bool] = None) -> AxisI
         axis_base = super().create(axis)
         if maybe_singleton is None:
             if isinstance(axis, Axis):
-                maybe_singleton = False
+                maybe_singleton = axis.type in ("batch", "channel", "index")
             elif isinstance(axis, str):
-                maybe_singleton = axis == "b"
+                maybe_singleton = axis in ("b", "c", "i")
             else:
                 if axis.size is None:
                     maybe_singleton = True
                 elif isinstance(axis.size, int):
                     maybe_singleton = axis.size == 1
                 elif isinstance(axis.size, v0_5.SizeReference):
                     maybe_singleton = (
-                        False  # TODO: check if singleton is ok for a `SizeReference`
+                        True  # TODO: check if singleton is ok for a `SizeReference`
                     )
                 elif isinstance(
                     axis.size, (v0_5.ParameterizedSize, v0_5.DataDependentSize)