Apply suggestions from code review

Co-authored-by: Elliott Sales de Andrade <[email protected]>

Author: timhoffm

lib/matplotlib/colors.py

@@ -953,8 +953,7 @@ def with_alpha(self, alpha):
              The alpha blending value, between 0 (transparent) and 1 (opaque).
         """
         if not isinstance(alpha, Real):
-            raise TypeError(
-                f"'alpha' must be numeric or None, not {type(alpha)}")
+            raise TypeError(f"'alpha' must be numeric or None, not {type(alpha)}")
         if not 0 <= alpha <= 1:
             ValueError("'alpha' must be between 0 and 1, inclusive")
         new_cm = self.copy()

lib/matplotlib/tests/test_colors.py

@@ -253,7 +253,7 @@ def test_colormap_with_alpha():
     cmap2 = cmap.with_alpha(0.5)
     # color is the same:
     vals = [0, 0.5, 1]  # numeric positions that map to the listed colors
-    assert_array_equal(cmap(vals)[:, :2], cmap2(vals)[:, :2])
+    assert_array_equal(cmap(vals)[:, :3], cmap2(vals)[:, :3])
     # alpha of cmap2 is changed:
     assert_array_equal(cmap(vals)[:, 3], [1, 1, 0.8])
     assert_array_equal(cmap2(vals)[:, 3], [0.5, 0.5, 0.5])