code: function extractStateVariables (contractName, sourcesList) {
    var states = astHelper.extractStatesDefinitions(sourcesList)
    if (!states[contractName]) {
      return []
    }
    var types = states[contractName].stateVariables
    var offsets = decodeInfo.computeOffsets(types, states, contractName, 'storage')
    if (!offsets) {
      return [] // TODO should maybe return an error
    }
    return offsets.typesOffsets
  }
docs: return all storage location variables of the given @arg contractName
  
  @param {String} contractName  - name of the contract
  @param {Object} sourcesList  - sources list
  @return {Object} - return the location of all contract variables in the storage