'@param message: An L{IMessagePart} provider which this structure object
reports on.
@param subtype: A L{str} giving the MIME subtype of the message (for
example, C{"plain"}).
@param attrs: A C{dict} giving the parameters of the I{Content-Type}
header of the message.'

def __init__(self, message, subtype, attrs):

    _MessageStructure.__init__(self, message, attrs)
    self.subtype = subtype
