'This constructor adds a Content-Type: and a MIME-Version: header.
The Content-Type: header is taken from the _maintype and _subtype
arguments.  Additional parameters for this header are taken from the
keyword arguments.'

def __init__(self, _maintype, _subtype, **_params):

    message.Message.__init__(self)
    ctype = ('%s/%s' % (_maintype, _subtype))
    self.add_header('Content-Type', ctype, **_params)
    self['MIME-Version'] = '1.0'
