ValueError: setting an array element with a sequence, RandomForestRegressor

Question

c, p = 0.5, 1
T=1000
n=500
z_tree = np.zeros(T)
for t in range(T):
    w = np.zeros(n)
    model_tree = pe.ConcreteModel()

    model_tree.z = pe.Var(domain=pe.NonNe