Re-use existing mapping in normalize_subscript if names are Names.

This avoids having to generate a redundant positional index. It will
modify any Names by reference, but I suppose that's fine, as the
reverse mapping inside Names is transparent to the user anyway.

src/biocutils/normalize_subscript.py

@@ -1,6 +1,8 @@
 from typing import Optional, Sequence, Tuple, Union
 import numpy
 
+from .Names import Names
+
 
 def _raise_int(idx: int, length):
     raise IndexError("subscript (" + str(idx) + ") out of range for vector-like object of length " + str(length))
@@ -119,11 +121,16 @@ def normalize_subscript(
     output = []
     has_strings = set()
     string_positions = []
+    are_names_indexed = isinstance(names, Names)
+
     for i, x in enumerate(sub):
         if isinstance(x, str):
-            has_strings.add(x)
-            string_positions.append(len(output))
-            output.append(None)
+            if are_names_indexed:
+                output.append(names.map(x))
+            else:
+                has_strings.add(x)
+                string_positions.append(len(output))
+                output.append(None)
         elif _is_scalar_bool(x):
             if x:
                 output.append(i)

tests/test_normalize_subscript.py

@@ -1,4 +1,4 @@
-from biocutils import normalize_subscript
+from biocutils import normalize_subscript, Names
 import pytest
 import numpy
 
@@ -95,6 +95,10 @@ def test_normalize_subscript_chaos():
         [1, 1, 3, 2, 5, 3, 0],
         False,
     )
+    assert normalize_subscript(["B", 1, "D", 2, "F", 3, "A"], 6, Names(names)) == (
+        [1, 1, 3, 2, 5, 3, 0],
+        False,
+    )
     assert normalize_subscript(
         ["B", 1, "A", 2, "B", 3, "A"], 6, ["A", "B", "A", "B", "A", "B"]
     ) == (