Removes all of the stimuli from the stimulus frames list.
<likert>
<trial>
None.
The following clears all of the stimuli from a trial:
<trial sometrial>
/ ontrialend= [trial.sometrial.clearstimulusframes();]
</trial>
The following clears all of the stimuli from surveypage:
<surveypage somepage>
/ ontrialend= [surveypage.somepage.clearstimulusframes();]
</trial>