<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def getParameterArrayCount(self, name, index):
 """Default implementation that return the length of the attribute. This default implementation goes hand in hand with :meth:`~nupic.bindings.regions.PyRegion.PyRegion.getParameterArray`. If you override one of them in your subclass, you should probably override both of them. The implementation prevents accessing parameters names that start with ``_``. It may be better to enforce this convention at the node spec level. :param name: (string) name of requested parameter :param index: (int) index of node inside the region (if relevant) :raises: Exception if parameter starts with ``_``. """

    if name.startswith('_'):
      raise Exception('Parameter name must not start with an underscore')

    return len(self.parameters[name])