docs: def valuefrompostdata(self, postdata):
          """This parameter method searches the POST data and retrieves the values it needs. It does not set the value yet though, but simply returns it. Needs to be explicitly passed to parameter.set()"""
          if self.multi: #multi parameters can be passed as  parameterid=choiceid1,choiceid2 or by setting parameterid[choiceid]=1 (or whatever other non-zero value)
              found = False
              if self.id in postdata:
                  found = True
                  passedvalues = postdata[self.id].split(',')
                  values = []
                  for choicekey in [x[0] for x in self.choices]:
                      if choicekey in passedvalues:
                          found = True
                          values.append(choicekey)
              else:
                  values = []
                  for choicekey in [x[0] for x in self.choices]:
                      if self.id+'['+choicekey+']' in postdata:
                          found = True
                          if postdata[self.id+'['+choicekey+']']:
                              values.append(choicekey)
              if not found:
                  return None
              else:
                  return values
          else:
              if self.id in postdata:
                  return postdata[self.id]
              else:
                  return None