<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def sha256sum(path, blocksize=65536):
 """ Computes the SHA256 signature of a file to verify that the file has not been modified in transit and that it is the correct version of the data. """

    sig = hashlib.sha256()
    with open(path, 'rb') as f:
        buf = f.read(blocksize)
        while len(buf) > 0:
            sig.update(buf)
            buf = f.read(blocksize)
    return sig.hexdigest()