Remove @overload and add new test

Author: Agent-Hellboy

integration_tests/test_str_01.py

@@ -38,28 +38,41 @@ def test_str_slice():
     # assert a[0:5:-1] == ""
 
 def test_str_isalpha():
-    a:str = "helloworld"
-    b:str = "hj kl"
+    a: str = "helloworld"
+    b: str = "hj kl"
+    c: str = "a12(){}A"
     res: bool = a.isalpha()
     res2: bool = b.isalpha()
+    res3: bool = c.isalpha()
     assert res == True 
     assert res2 == False
+    assert res3 == False
+
 
 def test_str_title():
-    a:str = "hello world"
-    b:str = "hj'kl"
+    a: str = "hello world"
+    b: str = "hj'kl"
+    c: str = "hELlo wOrlD"
+    d: str = "{Hel1o}world"
     res: str = a.title()
     res2: str = b.title()
+    res3: str = c.title()
+    res4: str = d.title()
     assert res == "Hello World" 
     assert res2 == "Hj'Kl"
+    assert res3 == "Hello World"
+    assert res4 == "{Hel1O}World"
 
 def test_str_istitle():
-    a:str = "Hello World"
-    b:str = "Hj'kl"
+    a: str = "Hello World"
+    b: str = "Hj'kl"
+    c: str = "hELlo wOrlD"
     res: bool = a.istitle()
     res2: bool = b.istitle()
+    res3: bool = c.istitle()
     assert res == True
     assert res2 == False 
+    assert res3 == False
 
 def test_str_repeat():
     a: str

src/runtime/lpython_builtin.py

@@ -685,7 +685,6 @@ def _lpython_str_join(s:str, lis:list[str]) -> str:
         res += s + lis[i]
     return res
 
-@overload
 def _lpython_str_isalpha(s: str) -> bool:
     ch: str
     for ch in s:
@@ -697,7 +696,6 @@ def _lpython_str_isalpha(s: str) -> bool:
         return False
     return True
 
-@overload
 def _lpython_str_title(s: str) -> str:
     result: str = ""
     capitalize_next: bool = True
@@ -722,7 +720,6 @@ def _lpython_str_title(s: str) -> str:
 
     return result
 
-@overload
 def _lpython_str_istitle(s: str) -> bool:
     length: i32 = len(s)