code: def compile(self, cost, name_scope="train"):
          
          with tf.name_scope(name_scope):
              return self.opt_.minimize(cost)
docs: Compile the optimizer with the given training parameters.
  
          Parameters
          ----------
          cost : Tensor
              A Tensor containing the value to minimize.
          name_scope : str , optional (default="train")
              Optional name scope for the optimizer graph ops.