fts.create_rule('First Rule', PolygonSymbolizer)
mysld.NamedLayer.UserStyle.FeatureTypeStyle.Rules[0
    ].PolygonSymbolizer.Fill.CssParameters[0].Value = '#000080'
mysld.NamedLayer.UserStyle.FeatureTypeStyle.Rules[0
    ].PolygonSymbolizer.Stroke.CssParameters[0].Value = '#FFFFFF'
mysld.NamedLayer.UserStyle.FeatureTypeStyle.Rules[0
    ].PolygonSymbolizer.Stroke.CssParameters[1].Value = '2'
Добавить новый фильтр в SLD