code: def union(left, right, distinct=False):
      
      left, right = _make_different_sources(left, right)
      return UnionCollectionExpr(_lhs=left, _rhs=right, _distinct=distinct)
docs: Union two collections.
  
      :param left: left collection
      :param right: right collection
      :param distinct:
      :return: collection
  
      :Example:
      >>> df['name', 'id'].union(df2['id', 'name'])