<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def compute_payload_block_hash(this):
 """Compute hash of each payload block. Used to prevent payload corruption and tampering."""


    return hmac.new(
        hashlib.sha512(
            struct.pack('<Q', this._index) +
            hashlib.sha512(
                this._._.header.value.dynamic_header.master_seed.data +
                this._.transformed_key + b'\x01'
            ).digest()
        ).digest(),
        struct.pack('<Q', this._index) +
        struct.pack('<I', len(this.block_data)) +
        this.block_data, hashlib.sha256
    ).digest()