May I ask the derivation process of the policy gradient theorem of reinforcement learning is the above

The derivation process of the policy gradient theorem of reinforcement learning is derived based on Markov decision process (MDP) and probability theory. Its derivation steps are: 1) Define state space S, behavior space A, discount factor γ and reward function R; 2) Construct state-value function V(s); 3) Solve the expected value of state-value function V(s); 4 ) Construct the policy function π(s); 5) Solve the expected value of the policy function π(s); 6) Deduce the policy gradient theorem.