diff --git a/.gitignore b/.gitignore
index 40d7f14..4851d92 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,6 @@
 .DS_Store
 .vscode/
+.idea/
 
 # Byte-compiled / optimized / DLL files
 __pycache__/
@@ -154,10 +155,3 @@ dmypy.json
 
 # Cython debug symbols
 cython_debug/
-
-# PyCharm
-#  JetBrains specific template is maintained in a separate JetBrains.gitignore that can
-#  be found at https://github.com/github/gitignore/blob/main/Global/JetBrains.gitignore
-#  and can be added to the global gitignore or merged into this file.  For a more nuclear
-#  option (not recommended) you can uncomment the following to ignore the entire idea folder.
-#.idea/
diff --git a/prymer/api/picking.py b/prymer/api/picking.py
index e407f8b..c4a0536 100644
--- a/prymer/api/picking.py
+++ b/prymer/api/picking.py
@@ -16,7 +16,7 @@
     from individual left and primers.
 
 """
-
+from collections.abc import Sequence
 from pathlib import Path
 from typing import Iterator
 from typing import Optional
@@ -91,8 +91,8 @@ def score(
 
 
 def build_primer_pairs(
-    left_primers: list[Oligo],
-    right_primers: list[Oligo],
+    left_primers: Sequence[Oligo],
+    right_primers: Sequence[Oligo],
     target: Span,
     amplicon_sizes: MinOptMax[int],
     amplicon_tms: MinOptMax[float],