import hashlib


def sha1sum(filename: str) -> str:
    """
    Generate a SHA1 hash of the provided file.

    Args:
        filename:
            Absolute path to file to hash as `str`

    Returns:
        SHA-1 hash
    """
    h = hashlib.sha1()
    with open(filename, 'rb') as f:
        for byte_block in iter(lambda: f.read(4096), b""):
            h.update(byte_block)
    return h.hexdigest()