def METHOD_NAME(self):
    str = self.typeheader
    if str is None:
        str = 'text/plain'
    if ';' in str:
        i = str.index(';')
        self.plisttext = str[i:]
        str = str[:i]
    else:
        self.plisttext = ''
    fields = str.split('/')
    for i in range(len(fields)):
        fields[i] = fields[i].strip().lower()
    self.type = '/'.join(fields)
    self.maintype = fields[0]
    self.subtype = '/'.join(fields[1:])