def convert_ams_classes(document):
tc = document.textclass
if (tc != "amsart" and tc != "amsart-plain" and
- tc == "amsart-seq" and tc == "amsbook"):
+ tc != "amsart-seq" and tc != "amsbook"):
return
if tc == "amsart-plain":
document.textclass = "amsart"