code: def from_master_secret_slow(cls, password, network=BitcoinMainNet):
          
          # Make sure the password string is bytes
          key = ensure_bytes(password)
          data = unhexlify(b"0" * 64)  # 256-bit 0
          for i in range(50000):
              data = hmac.new(key, msg=data, digestmod=sha256).digest()
          return cls.from_master_secret(data, network)
docs: Generate a new key from a password using 50,000 rounds of HMAC-SHA256.
  
          This should generate the same result as bip32.org.
  
          WARNING: The security of this method has not been evaluated.