def save(filename, contents, include_params=False, variable_batch_size=True):
    '''Save network definition, inference/training execution
    configurations etc.

    Args:
        filename (str): Filename to store information. The file
            extension is used to determine the saving file format.
            ``.nnp``: (Recommended) Creating a zip archive with nntxt (network
            definition etc.) and h5 (parameters).
            ``.nntxt``: Protobuf in text format.
            ``.protobuf``: Protobuf in binary format (unsafe in terms of
             backward compatibility).
        contents (dict): Information to store.
        include_params (bool): Includes parameter into single file. This is
            ignored when the extension of filename is nnp.
        variable_batch_size (bool):
            By ``True``, the first dimension of all variables is considered
            as batch size, and left as a placeholder
            (more specifically ``-1``). The placeholder dimension will be
            filled during/after loading.

    Example:
        The following example creates a two inputs and two
        outputs MLP, and save the network structure and the initialized
        parameters.

        .. code-block:: python

            import nnabla as nn
            import nnabla.functions as F
            import nnabla.parametric_functions as PF
            from nnabla.utils.save import save

            batch_size = 16
            x0 = nn.Variable([batch_size, 100])
            x1 = nn.Variable([batch_size, 100])
            h1_0 = PF.affine(x0, 100, name='affine1_0')
            h1_1 = PF.affine(x1, 100, name='affine1_0')
            h1 = F.tanh(h1_0 + h1_1)
            h2 = F.tanh(PF.affine(h1, 50, name='affine2'))
            y0 = PF.affine(h2, 10, name='affiney_0')
            y1 = PF.affine(h2, 10, name='affiney_1')

            contents = {
                'networks': [
                    {'name': 'net1',
                     'batch_size': batch_size,
                     'outputs': {'y0': y0, 'y1': y1},
                     'names': {'x0': x0, 'x1': x1}}],
                'executors': [
                    {'name': 'runtime',
                     'network': 'net1',
                     'data': ['x0', 'x1'],
                     'output': ['y0', 'y1']}]}
            save('net.nnp', contents)


        To get a trainable model, use following code instead.

        .. code-block:: python

            contents = {
            'global_config': {'default_context': ctx},
            'training_config':
                {'max_epoch': args.max_epoch,
                 'iter_per_epoch': args_added.iter_per_epoch,
                 'save_best': True},
            'networks': [
                {'name': 'training',
                 'batch_size': args.batch_size,
                 'outputs': {'loss': loss_t},
                 'names': {'x': x, 'y': t, 'loss': loss_t}},
                {'name': 'validation',
                 'batch_size': args.batch_size,
                 'outputs': {'loss': loss_v},
                 'names': {'x': x, 'y': t, 'loss': loss_v}}],
            'optimizers': [
                {'name': 'optimizer',
                 'solver': solver,
                 'network': 'training',
                 'dataset': 'mnist_training',
                 'weight_decay': 0,
                 'lr_decay': 1,
                 'lr_decay_interval': 1,
                 'update_interval': 1}],
            'datasets': [
                {'name': 'mnist_training',
                 'uri': 'MNIST_TRAINING',
                 'cache_dir': args.cache_dir + '/mnist_training.cache/',
                 'variables': {'x': x, 'y': t},
                 'shuffle': True,
                 'batch_size': args.batch_size,
                 'no_image_normalization': True},
                {'name': 'mnist_validation',
                 'uri': 'MNIST_VALIDATION',
                 'cache_dir': args.cache_dir + '/mnist_test.cache/',
                 'variables': {'x': x, 'y': t},
                 'shuffle': False,
                 'batch_size': args.batch_size,
                 'no_image_normalization': True
                 }],
            'monitors': [
                {'name': 'training_loss',
                 'network': 'validation',
                 'dataset': 'mnist_training'},
                {'name': 'validation_loss',
                 'network': 'validation',
                 'dataset': 'mnist_validation'}],
            }


    '''
    _, ext = os.path.splitext(filename)
    if ext == '.nntxt' or ext == '.prototxt':
        logger.info("Saving {} as prototxt".format(filename))
        proto = create_proto(contents, include_params, variable_batch_size)
        with open(filename, 'w') as file:
            text_format.PrintMessage(proto, file)
    elif ext == '.protobuf':
        logger.info("Saving {} as protobuf".format(filename))
        proto = create_proto(contents, include_params, variable_batch_size)
        with open(filename, 'wb') as file:
            file.write(proto.SerializeToString())
    elif ext == '.nnp':
        logger.info("Saving {} as nnp".format(filename))
        try:
            tmpdir = tempfile.mkdtemp()
            save('{}/network.nntxt'.format(tmpdir),
                 contents, include_params=False, variable_batch_size=variable_batch_size)

            with open('{}/nnp_version.txt'.format(tmpdir), 'w') as file:
                file.write('{}\n'.format(nnp_version()))

            save_parameters('{}/parameter.protobuf'.format(tmpdir))

            with zipfile.ZipFile(filename, 'w') as nnp:
                nnp.write('{}/nnp_version.txt'.format(tmpdir),
                          'nnp_version.txt')
                nnp.write('{}/network.nntxt'.format(tmpdir), 'network.nntxt')
                nnp.write('{}/parameter.protobuf'.format(tmpdir),
                          'parameter.protobuf')
        finally:
            shutil.rmtree(tmpdir)
Save network definition, inference/training execution
    configurations etc.

    Args:
        filename (str): Filename to store information. The file
            extension is used to determine the saving file format.
            ``.nnp``: (Recommended) Creating a zip archive with nntxt (network
            definition etc.) and h5 (parameters).
            ``.nntxt``: Protobuf in text format.
            ``.protobuf``: Protobuf in binary format (unsafe in terms of
             backward compatibility).
        contents (dict): Information to store.
        include_params (bool): Includes parameter into single file. This is
            ignored when the extension of filename is nnp.
        variable_batch_size (bool):
            By ``True``, the first dimension of all variables is considered
            as batch size, and left as a placeholder
            (more specifically ``-1``). The placeholder dimension will be
            filled during/after loading.

    Example:
        The following example creates a two inputs and two
        outputs MLP, and save the network structure and the initialized
        parameters.

        .. code-block:: python

            import nnabla as nn
            import nnabla.functions as F
            import nnabla.parametric_functions as PF
            from nnabla.utils.save import save

            batch_size = 16
            x0 = nn.Variable([batch_size, 100])
            x1 = nn.Variable([batch_size, 100])
            h1_0 = PF.affine(x0, 100, name='affine1_0')
            h1_1 = PF.affine(x1, 100, name='affine1_0')
            h1 = F.tanh(h1_0 + h1_1)
            h2 = F.tanh(PF.affine(h1, 50, name='affine2'))
            y0 = PF.affine(h2, 10, name='affiney_0')
            y1 = PF.affine(h2, 10, name='affiney_1')

            contents = {
                'networks': [
                    {'name': 'net1',
                     'batch_size': batch_size,
                     'outputs': {'y0': y0, 'y1': y1},
                     'names': {'x0': x0, 'x1': x1}}],
                'executors': [
                    {'name': 'runtime',
                     'network': 'net1',
                     'data': ['x0', 'x1'],
                     'output': ['y0', 'y1']}]}
            save('net.nnp', contents)


        To get a trainable model, use following code instead.

        .. code-block:: python

            contents = {
            'global_config': {'default_context': ctx},
            'training_config':
                {'max_epoch': args.max_epoch,
                 'iter_per_epoch': args_added.iter_per_epoch,
                 'save_best': True},
            'networks': [
                {'name': 'training',
                 'batch_size': args.batch_size,
                 'outputs': {'loss': loss_t},
                 'names': {'x': x, 'y': t, 'loss': loss_t}},
                {'name': 'validation',
                 'batch_size': args.batch_size,
                 'outputs': {'loss': loss_v},
                 'names': {'x': x, 'y': t, 'loss': loss_v}}],
            'optimizers': [
                {'name': 'optimizer',
                 'solver': solver,
                 'network': 'training',
                 'dataset': 'mnist_training',
                 'weight_decay': 0,
                 'lr_decay': 1,
                 'lr_decay_interval': 1,
                 'update_interval': 1}],
            'datasets': [
                {'name': 'mnist_training',
                 'uri': 'MNIST_TRAINING',
                 'cache_dir': args.cache_dir + '/mnist_training.cache/',
                 'variables': {'x': x, 'y': t},
                 'shuffle': True,
                 'batch_size': args.batch_size,
                 'no_image_normalization': True},
                {'name': 'mnist_validation',
                 'uri': 'MNIST_VALIDATION',
                 'cache_dir': args.cache_dir + '/mnist_test.cache/',
                 'variables': {'x': x, 'y': t},
                 'shuffle': False,
                 'batch_size': args.batch_size,
                 'no_image_normalization': True
                 }],
            'monitors': [
                {'name': 'training_loss',
                 'network': 'validation',
                 'dataset': 'mnist_training'},
                {'name': 'validation_loss',
                 'network': 'validation',
                 'dataset': 'mnist_validation'}],
            }