def METHOD_NAME(self, filename):
    """Read the file with the specified name and check its checksum
    against self.hexdigest.  Return True if they match, False
    otherwise.  Actual checksum is stored in self.sum.
    """
    self.sum = checksum(self.hash_fun, filename, block_size=self.block_size)
    return self.sum == self.hexdigest