code: def compute_header_hmac_hash(context):
      
  
      return hmac.new(
          hashlib.sha512(
              b'\xff' * 8 +
              hashlib.sha512(
                  context._.header.value.dynamic_header.master_seed.data +
                  context.transformed_key +
                  b'\x01'
              ).digest()
          ).digest(),
          context._.header.data,
          hashlib.sha256
      ).digest()
docs: Compute HMAC-SHA256 hash of header.
      Used to prevent header tampering.