def set_type(self, type, header='Content-Type', requote=True):
        """Set the main type and subtype for the Content-Type header.

        type must be a string in the form "maintype/subtype", otherwise a
        ValueError is raised.

        This method replaces the Content-Type header, keeping all the
        parameters in place.  If requote is False, this leaves the existing
        header's quoting as is.  Otherwise, the parameters will be quoted (the
        default).

        An alternative header can be specified in the header argument.  When
        the Content-Type header is set, we'll always also add a MIME-Version
        header.
        """
        # BAW: should we be strict?
        if not type.count('/') == 1:
            raise ValueError
        # Set the Content-Type, you get a MIME-Version
        if header.lower() == 'content-type':
            del self['mime-version']
            self['MIME-Version'] = '1.0'
        if header not in self:
            self[header] = type
            return
        params = self.get_params(header=header, unquote=requote)
        del self[header]
        self[header] = type
        # Skip the first param; it's the old type.
        for p, v in params[1:]:
            self.set_param(p, v, header, requote)
Set the main type and subtype for the Content-Type header.

        type must be a string in the form "maintype/subtype", otherwise a
        ValueError is raised.

        This method replaces the Content-Type header, keeping all the
        parameters in place.  If requote is False, this leaves the existing
        header's quoting as is.  Otherwise, the parameters will be quoted (the
        default).

        An alternative header can be specified in the header argument.  When
        the Content-Type header is set, we'll always also add a MIME-Version
        header.