S6:-Object-Oriented-Programming.md

@@ -100,7 +100,7 @@ print(f"    T: {seq_count_base(seq1, 'T')}")
 print(f"    C: {seq_count_base(seq1, 'C')}")
 print(f"    G: {seq_count_base(seq1, 'G')}")
 
-# -- But this program works normally. No error es detected
+# -- But this program works normally. No error is detected!
 ```
 
 * How could you solve that problem? How could we guarantee that the introduced sequence is valid?