SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 1)
    Function dictGetKeys (children 1)
     ExpressionList (children 3)
      Literal \'dict_types\'
      Literal \'arr_nested\'
      Literal Array_[Array_[UInt64_1, UInt64_2], Array_[UInt64_3]]
