code: func (klv *KeyLevelValidator) PreValidate(txNum uint64, block *common.Block) {
  	for i := int64(txNum); i >= 0; i-- {
  		txPosition := uint64(i)
  
  		klv.invokeOnce(block, txPosition).Do(
  			func() {
  				klv.extractDependenciesForTx(block.Header.Number, txPosition, block.Data.Data[txPosition])
  			})
  	}
  }
docs: // PreValidate implements the function of the StateBasedValidator interface