code: func (t *Transaction) Bind(name string, value interface{}) *Transaction {
  	if t.bindVars == nil {
  		t.bindVars = make(map[string]string)
  	}
  	m, _ := json.Marshal(value)
  	t.bindVars[name] = strings.Replace(string(m), `"`, "'", -1)
  	return t
  }
docs: // Bind sets the name and value of a bind parameter
  // Binding parameters prevents AQL injection
  // Example:
  // transaction := NewTransaction([]string{}, []string{}).
  // 		AddAQL("var1", "FOR d IN nodes FILTER d._key == @key RETURN d._id").
  // 		AddAQL("var2", "FOR n IN nodes FILTER n._id == {{.var1}}[0] RETURN n._key").Return("var2")
  // transaction.Bind("key", 123)
  //