code: function (params, funAbi, callback) {
      this.encodeParams(params, funAbi, (error, encodedParam) => {
        if (error) return callback(error)
        callback(null, { dataHex: helper.encodeFunctionId(funAbi) + encodedParam.dataHex, funAbi, funArgs: encodedParam.funArgs })
      })
    }
docs: encode function call (function id + encoded parameters)
  
  @param {Object} params    - input paramater of the function to call
  @param {Object} funAbi    - abi definition of the function to call. null if building data for the ctor.
  @param {Function} callback    - callback