code: def union(self, query, all=False):
          
          self.unions.append({
              'query': query,
              'all': all
          })
  
          return self.merge_bindings(query)
docs: Add a union statement to the query
  
          :param query: A QueryBuilder instance
          :type query: QueryBuilder
  
          :param all: Whether it is a "union all" statement
          :type all: bool
  
          :return: The query
          :rtype: QueryBuilder