Add assert to make sure tuple logic isn't removed.

Author: stefmolin

lib/matplotlib/tests/test_cbook.py

@@ -910,3 +910,4 @@ def test_safe_first_element_with_none():
 def test_auto_format_str(fmt, value, result):
     """Apply *value* to the format string *fmt*."""
     assert cbook._auto_format_str(fmt, value) == result
+    assert cbook._auto_format_str(fmt, np.float64(value)) == result