<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def file_checksum(filepath):
 """Calculate md5 checksum on file :param filepath: Full path to file (e.g. /home/stack/image.qcow2) :type filepath: string """

    checksum = hashlib.md5()
    with open(filepath, 'rb') as f:
        for fragment in iter(lambda: f.read(65536), ''):
            checksum.update(fragment)
    return checksum.hexdigest()