[utils] Allow partial application for more functions (#11391)

Also adds the `trim_str` traversal helper

Authored by: bashonly, Grub4K

Co-authored-by: Simon Sawicki <[email protected]>

test/test_traversal.py

@@ -12,9 +12,10 @@ from yt_dlp.utils import (
     str_or_none,
 )
 from yt_dlp.utils.traversal import (
-    traverse_obj,
     require,
     subs_list_to_dict,
+    traverse_obj,
+    trim_str,
 )
 
 _TEST_DATA = {
@@ -495,6 +496,20 @@ class TestTraversalHelpers:
             {'url': 'https://example.com/subs/en2', 'ext': 'ext'},
         ]}, '`quality` key should sort subtitle list accordingly'
 
+    def test_trim_str(self):
+        with pytest.raises(TypeError):
+            trim_str('positional')
+
+        assert callable(trim_str(start='a'))
+        assert trim_str(start='ab')('abc') == 'c'
+        assert trim_str(end='bc')('abc') == 'a'
+        assert trim_str(start='a', end='c')('abc') == 'b'
+        assert trim_str(start='ab', end='c')('abc') == ''
+        assert trim_str(start='a', end='bc')('abc') == ''
+        assert trim_str(start='ab', end='bc')('abc') == ''
+        assert trim_str(start='abc', end='abc')('abc') == ''
+        assert trim_str(start='', end='')('abc') == 'abc'
+
 
 class TestDictGet:
     def test_dict_get(self):