'Number of results to attempt to return on the initial request.
Raises:
datastore_errors.BadArgumentError if value is not an integer or is not
greater than zero.'

@datastore_rpc.ConfigOption
def prefetch_size(value):

    datastore_types.ValidateInteger(value, 'prefetch_size', datastore_errors.BadArgumentError, zero_ok=True)
    return value
