// retoor <retoor@molodetz.nl>
import "dataset" for Dataset
var ds = Dataset.memory()
var users = ds["users"]
users.insert({"name": "Alice"})
var cols1 = users.columns
System.print(cols1.containsKey("uid")) // expect: true
System.print(cols1.containsKey("name")) // expect: true
System.print(cols1.containsKey("email")) // expect: false
users.insert({"name": "Bob", "email": "bob@example.com"})
var cols2 = users.columns
System.print(cols2.containsKey("email")) // expect: true
ds.close()