'Create a copy of this instance object.'

def obj_clone(self):

    nobj = super(Instance, self).obj_clone()
    if hasattr(self, '_orig_metadata'):
        nobj._orig_metadata = dict(self._orig_metadata)
    if hasattr(self, '_orig_system_metadata'):
        nobj._orig_system_metadata = dict(self._orig_system_metadata)
    return nobj
