Unexpected output for string method on whitespace characters

When I run the following code:
```py
def f():
    b: str = " \t\n\v\f\r"
    print(b.isspace())
    print(b.islower())
    print(b.isupper())


f()
```

In Python:
```
True
False
False
```

In LPython:
```
False
True
False
```

Hence there is a bug in both the `isspace()` and the `islower()` methods.