diff --git a/ciphers/a1z26.py b/ciphers/a1z26.py
index a1377ea6d397..d99efe186519 100644
--- a/ciphers/a1z26.py
+++ b/ciphers/a1z26.py
@@ -13,7 +13,21 @@ def encode(plain: str) -> list[int]:
     """
     >>> encode("myname")
     [13, 25, 14, 1, 13, 5]
+    >>> encode("abCd")
+    Traceback (most recent call last):
+        ...
+    ValueError: plain must contain only lowercase letters (a-z)
+    >>> encode("n0w")
+    Traceback (most recent call last):
+        ...
+    ValueError: plain must contain only lowercase letters (a-z)
+    >>> encode("later!")
+    Traceback (most recent call last):
+        ...
+    ValueError: plain must contain only lowercase letters (a-z)
     """
+    if not plain.islower() or not plain.isalpha():
+        raise ValueError("plain must contain only lowercase letters (a-z)")
     return [ord(elem) - 96 for elem in plain]
 
 
diff --git a/machine_learning/sequential_minimum_optimization.py b/machine_learning/sequential_minimum_optimization.py
index 625fc28fe60c..e96f06d6f080 100644
--- a/machine_learning/sequential_minimum_optimization.py
+++ b/machine_learning/sequential_minimum_optimization.py
@@ -451,7 +451,7 @@ def test_cancer_data():
     print("Hello!\nStart test SVM using the SMO algorithm!")
     # 0: download dataset and load into pandas' dataframe
     if not os.path.exists(r"cancer_data.csv"):
-        request = urllib.request.Request(  # noqa: S310
+        request = urllib.request.Request(
             CANCER_DATASET_URL,
             headers={"User-Agent": "Mozilla/4.0 (compatible; MSIE 5.5; Windows NT)"},
         )