read a binary file to find its type

[atux_null]

Hi. i think i got it somewhere wrong and i will start over. I 've been given a file named whatever and it does not have any file extension. My task is to write a program to read its first bytes and see if it is jpeg or not. Also print the first 3 bytes values in hex and in int format.
up to now i have

with open('whatever', 'rb') as fd:
    file_head = fd.read(3)
Anumbers = {'jpeg': bytes([0xFF,0xD8,0xFF])}
max_read_size = max(len(m) for m in Anumbers.values()) 
 
with open('whatever', 'rb') as fd:
    file_head = fd.read(max_read_size)
 
if file_head.startswith(Anumbers['jpeg']):
    print("It's not a JPEG file")
else:
    print("It's a JPEG file")

also i've told that this file probably is not a jpeg, but i am not sure. Some help please?