# Palindrome Check

Write a function that checks if a given string is a palindrome. Consider only alphanumeric characters and ignore case.

## Function Signature

```python
def is_palindrome(s: str) -> bool:
```

## Parameters
- `s` — a string to check

## Returns
- `True` if the string is a palindrome, `False` otherwise

## Examples

```
is_palindrome("racecar") -> True
is_palindrome("A man, a plan, a canal: Panama") -> True
is_palindrome("hello") -> False
is_palindrome("") -> True
```
