tf.placeholder(tf.float32, (N,2)) // para1: data type para2: data shape
tf.Variable(tf.random_normal(2,1)) //notice: V is capital letter & its initialize need to do at the end or during run()
using tf.global_variable_initializer() to initialinze all the variables
tf.squeeze(input) //remove all the value equal to 1
tf.sigmoid(input) //calculate the sigmoid value using y = 1/(1 + exp (-x)), exp(x) = e
tf.round(input) //四捨五入到最接近的整數
tf.reduce_sum(input) // get the sum value of the inputs