CLN: do not import Axes/Artist/Figure from matplotlib.pyplot (#55192)

CLN: do not import Axes/Artist from matplotlib.pyplot

Author: twoertwein

pandas/_testing/asserters.py

@@ -416,22 +416,23 @@ def assert_attr_equal(attr: str, left, right, obj: str = "Attributes") -> None:
 
 
 def assert_is_valid_plot_return_object(objs) -> None:
- import matplotlib.pyplot as plt
+ from matplotlib.artist import Artist
+ from matplotlib.axes import Axes
 
  if isinstance(objs, (Series, np.ndarray)):
  for el in objs.ravel():
  msg = (
  "one of 'objs' is not a matplotlib Axes instance, "
  f"type encountered {repr(type(el).__name__)}"
  )
- assert isinstance(el, (plt.Axes, dict)), msg
+ assert isinstance(el, (Axes, dict)), msg
  else:
  msg = (
  "objs is neither an ndarray of Artist instances nor a single "
  "ArtistArtist instance, tuple, or dict, 'objs' is a "
  f"{repr(type(objs).__name__)}"
  )
- assert isinstance(objs, (plt.Artist, tuple, dict)), msg
+ assert isinstance(objs, (Artist, tuple, dict)), msg
 
 
 def assert_is_sorted(seq) -> None: