* 示例1（输入为2-D Tensor）：

    输入：
        X.shape = [3, 5]
        X.data = [[0, 1, 2, 0, 0],
                  [0, 3, 4, 0, 0],
                  [0, 0, 0, 0, 0]]

    参数：
        shape = [2, 2]
        offsets = [0, 1]

    输出：
        Out.shape = [2, 2]
        Out.data = [[1, 2],
                    [3, 4]]

* 示例2（输入为3-D Tensor）：

    输入：

        X.shape = [2, 3, 4]
        X.data =  [[[0, 1, 2, 3],
                    [0, 5, 6, 7],
                    [0, 0, 0, 0]],
                   [[0, 3, 4, 5],
                    [0, 6, 7, 8],
                    [0, 0, 0, 0]]]

    参数：
        shape = [2, 2, -1]
        offsets = [0, 0, 1]

    输出：
        Out.shape = [2, 2, 3]
        Out.data = [[[1, 2, 3],
                     [5, 6, 7]],
                    [[3, 4, 5],
                     [6, 7, 8]]]

import paddle.fluid as fluid
x = fluid.data(name="x", shape=[None, 3, 5], dtype="float32")
# x.shape = [-1, 3, 5], where -1 indicates batch size, and it will get the exact value in runtime.

# shape is a 1-D Tensor
crop_shape = fluid.data(name="crop_shape", shape=[3], dtype="int32")
crop0 = fluid.layers.crop_tensor(x, shape=crop_shape)
# crop0.shape = [-1, -1, -1], it means crop0.shape[0] = x.shape[0] in runtime.

# or shape is a list in which each element is a constant
crop1 = fluid.layers.crop_tensor(x, shape=[-1, -1, 3], offsets=[0, 1, 0])
# crop1.shape = [-1, 2, 3]

# or shape is a list in which each element is a constant or Tensor
y = fluid.data(name="y", shape=[3, 8, 8], dtype="float32")
dim1 = fluid.layers.data(name="dim1", shape=[1], dtype="int32")
crop2 = fluid.layers.crop_tensor(y, shape=[3, dim1, 4])
# crop2.shape = [3, -1, 4]

# offsets is a 1-D Tensor
crop_offsets = fluid.data(name="crop_offsets", shape=[3], dtype="int32")
crop3 = fluid.layers.crop_tensor(x, shape=[-1, 2, 3], offsets=crop_offsets)
# crop3.shape = [-1, 2, 3]

# offsets is a list in which each element is a constant or Tensor
offsets_var =  fluid.data(name="offset", shape=[1], dtype="int32")
crop4 = fluid.layers.crop_tensor(x, shape=[-1, 2, 3], offsets=[0, 1, offsets_var])
# crop4.shape = [-1, 2, 3]