Simplify parameter handling in FloatingAxesBase.

- `grid_helper` can just become a standard kwonly arg.
- `GridHelperCurveLinear` is the only class that defines `get_boundary`,
  so in practice the hasattr check is the same as an isinstance check.
  (It is technically possible that someone wrote their own
  GridHelperCurveLinear-like subclass with the same API, but let's not
  overly worry about that... and they can always still completely
  inherit GridHelperCurveLinear and full override everything if really
  needed.)

Author: anntzer

lib/mpl_toolkits/axisartist/floating_axes.py

@@ -8,9 +8,9 @@
 import numpy as np
 
 from matplotlib import _api, cbook
+import matplotlib.axes as maxes
 import matplotlib.patches as mpatches
 from matplotlib.path import Path
-import matplotlib.axes as maxes
 
 from mpl_toolkits.axes_grid1.parasite_axes import host_axes_class_factory
 
@@ -311,13 +311,9 @@ def get_boundary(self):
 
 class FloatingAxesBase:
 
-    def __init__(self, *args, **kwargs):
-        grid_helper = kwargs.get("grid_helper", None)
-        if grid_helper is None:
-            raise ValueError("FloatingAxes requires grid_helper argument")
-        if not hasattr(grid_helper, "get_boundary"):
-            raise ValueError("grid_helper must implement get_boundary method")
-        super().__init__(*args, **kwargs)
+    def __init__(self, *args, grid_helper, **kwargs):
+        _api.check_isinstance(GridHelperCurveLinear, grid_helper=grid_helper)
+        super().__init__(*args, grid_helper=grid_helper, **kwargs)
         self.set_aspect(1.)
         self.adjust_axes_lim()