fix early matplotlib import

Author: JoelLucaAdams

src/sdf_xarray/dataarray_accessor.py

@@ -1,11 +1,16 @@
+from __future__ import annotations
+
 from types import MethodType
+from typing import TYPE_CHECKING
 
 import xarray as xr
-from matplotlib.animation import FuncAnimation
 from xarray.plot.accessor import DataArrayPlotAccessor
 
 from .plotting import animate, show
 
+if TYPE_CHECKING:
+    from matplotlib.animation import FuncAnimation
+
 
 @xr.register_dataarray_accessor("epoch")
 class EpochAccessor: