def get_extension(self, publisher_name, extension_name, version=None, flags=None, account_token=None, account_token_header=None):
        """GetExtension.
        [Preview API]
        :param str publisher_name:
        :param str extension_name:
        :param str version:
        :param str flags:
        :param str account_token:
        :param String account_token_header: Header to pass the account token
        :rtype: :class:`<PublishedExtension> <azure.devops.v5_1.gallery.models.PublishedExtension>`
        """
        route_values = {}
        if publisher_name is not None:
            route_values['publisherName'] = self._serialize.url('publisher_name', publisher_name, 'str')
        if extension_name is not None:
            route_values['extensionName'] = self._serialize.url('extension_name', extension_name, 'str')
        query_parameters = {}
        if version is not None:
            query_parameters['version'] = self._serialize.query('version', version, 'str')
        if flags is not None:
            query_parameters['flags'] = self._serialize.query('flags', flags, 'str')
        if account_token is not None:
            query_parameters['accountToken'] = self._serialize.query('account_token', account_token, 'str')
        response = self._send(http_method='GET',
                              location_id='e11ea35a-16fe-4b80-ab11-c4cab88a0966',
                              version='5.1-preview.2',
                              route_values=route_values,
                              query_parameters=query_parameters)
        return self._deserialize('PublishedExtension', response)
GetExtension.
        [Preview API]
        :param str publisher_name:
        :param str extension_name:
        :param str version:
        :param str flags:
        :param str account_token:
        :param String account_token_header: Header to pass the account token
        :rtype: :class:`<PublishedExtension> <azure.devops.v5_1.gallery.models.PublishedExtension>`