code: function(privateKey, cb = null){
          if(isFunction(cb)){
              try {
                  return cb(null, ethUtils.privateToPublic(privateKey))
              }
              catch(err){
                  return cb(err)
              }
          } else {
              try {
                  return ethUtils.privateToPublic(privateKey)
              }
              catch(err){
                  return err
              }
          }
      }
docs: get public key for a given ethereum private key
  @param  {Buffer} privateKey ethereum private key
  @return {Buffer}            the associated public key