code: def add_filter(self, key, filter_value):
          
          seek = u"filter[%s]" % key
          if self.validate_filter(key, filter_value):
              self.filters[key] = filter_value
              return True
          else:
              msg = u'Invalid filter value: filter:%s value:%s' % (key, filter_value)
              print msg
              raise SalesKingException("FILTER_INVALID", msg )
docs: add and validate a filter with value
          returns True on success otherwise exception