How to use the arms.three_link.arm.Arm function in arms

plt.xlabel('Training iterations')
    plt.ylabel('Error')
    plt.yscale('log')

    # load in the weights and see how well they control the arm
    dt = 1e-2
    sig_len = 40

    # HACK: append system path to have access to the arm code
    # NOTE: Change this path to wherever your plant model is kept!
    sys.path.append("../../../studywolf_control/studywolf_control/")
    # from arms.two_link.arm_python import Arm as Arm
    from arms.three_link.arm import Arm as Arm
    if verbose:
        print('Plant is: %s' % str(Arm))
    arm = Arm(dt=dt)

    from hessianfree import RNNet
    from hessianfree.nonlinearities import (Tanh, Linear)
    from train_hf_3link import PlantArm, gen_targets

    rec_coeff = [1, 1]
    rec_type = "sparse"
    eps = 1e-6

    num_states = arm.DOF * 2
    targets = gen_targets(arm, sig_len=sig_len)
    init_state = np.zeros((len(targets), num_states), dtype=np.float32)
    init_state[:, :arm.DOF] = arm.init_q # set up the initial joint angles
    plant = PlantArm(arm, targets=targets,
                     init_state=init_state, eps=eps)

plt.title('AHF training error')
    plt.xlabel('Training iterations')
    plt.ylabel('Error')
    plt.yscale('log')

    # load in the weights and see how well they control the arm
    dt = 1e-2
    sig_len = 40

    # HACK: append system path to have access to the arm code
    # NOTE: Change this path to wherever your plant model is kept!
    sys.path.append("../../../studywolf_control/studywolf_control/")
    # from arms.two_link.arm_python import Arm as Arm
    from arms.three_link.arm import Arm as Arm
    if verbose:
        print('Plant is: %s' % str(Arm))
    arm = Arm(dt=dt)

    from hessianfree import RNNet
    from hessianfree.nonlinearities import (Tanh, Linear)
    from train_hf_3link import PlantArm, gen_targets

    rec_coeff = [1, 1]
    rec_type = "sparse"
    eps = 1e-6

    num_states = arm.DOF * 2
    targets = gen_targets(arm, sig_len=sig_len)
    init_state = np.zeros((len(targets), num_states), dtype=np.float32)
    init_state[:, :arm.DOF] = arm.init_q # set up the initial joint angles
    plant = PlantArm(arm, targets=targets,
                     init_state=init_state, eps=eps)