old_contents: from plenum.common.messages.fields import ProtocolVersionField
  from plenum.common.plenum_protocol_version import PlenumProtocolVersion
  
  validator = ProtocolVersionField()
  
  
  def test_valid():
      assert not validator.validate(1)
      assert not validator.validate(PlenumProtocolVersion.STATE_PROOF_SUPPORT.value)
      assert not validator.validate(None)  # version can be None (for backward compatibility)
  
  
  def test_invalid():
      assert validator.validate(3)
      assert validator.validate("1")
      assert validator.validate("")
      assert validator.validate(0)
      assert validator.validate(1.0)
      assert validator.validate(0.1)
  
new_contents: from plenum.common.messages.fields import ProtocolVersionField
  from plenum.common.plenum_protocol_version import PlenumProtocolVersion
  
  validator = ProtocolVersionField()
  
  
  def test_valid():
      assert not validator.validate(1)
      assert not validator.validate(2)
      assert not validator.validate(PlenumProtocolVersion.STATE_PROOF_SUPPORT.value)
      assert not validator.validate(PlenumProtocolVersion.TXN_FORMAT_1_0_SUPPORT.value)
      assert not validator.validate(None)  # version can be None (for backward compatibility)
  
  
  def test_invalid():
      assert validator.validate(3)
      assert validator.validate("1")
      assert validator.validate("")
      assert validator.validate(0)
      assert validator.validate(1.0)
      assert validator.validate(0.1)
  
subject: Fix tests