code: def _table_union(left, right, distinct=False):
      
      op = ops.Union(left, right, distinct=distinct)
      return op.to_expr()
docs: Form the table set union of two table expressions having identical
      schemas.
  
      Parameters
      ----------
      right : TableExpr
      distinct : boolean, default False
          Only union distinct rows not occurring in the calling table (this
          can be very expensive, be careful)
  
      Returns
      -------
      union : TableExpr