Simple image format detector for images from Tumblr

from pathlib import Path

__all__ = ["detect_format"]

def detect_format(file_path):
    if not isinstance(file_path, Path):
        raise TypeError("Image file passed to format detector must be a Path")

    with file_path.open("rb") as handler:
        header = handler.read(32)

    # JPEG data in JFIF or Exif format
    if header[6:10] in (b"JFIF", b"Exif"):
        return ".jpg"

    # GIF-87 and GIF-89
    if header[0:6] in (b"GIF87a", b"GIF89a"):
        return ".gif"

    # Regular PNG image
    if header[0:8] == b"\211PNG\r\n\032\n":
        return ".png"

    # WebP
    if header[0:4] == b"RIFF" and h[8:12] == b"WEBP":
        return ".webp"

    # Couldn't detect anything, falling back to just returning suffix
    return file_path.suffix