def __init__(self, source, type, vals):
    "source is a RowSource or None if it isn't from a table"
    if len(type) != len(vals):
      raise ValueError('type/vals length mismatch', len(type), len(vals))
    self.source, self.type, self.vals = source, type, vals
def __init__ ( self , source , type , vals ) : if len ( type ) != len ( vals ) : raise ValueError ( 'type/vals length mismatch' , len ( type ) , len ( vals ) ) self . source , self . type , self . vals = source , type , vals
source is a RowSource or None if it isn't from a table