Current, when we like to hide a field, we do:
def _setup__(cls): super(cls).__setup__() cls.field_name.states['invisible'] = True
Also we need a extra task: hide the label in XML form view:
<xpath expr="/form/notebook/page[@id='xxxxx']/label[@name='field_name']" position="replace"></xpath>
IMHO when hide a field, also we need to hide the label.