def METHOD_NAME(self, *args, **kwargs):
    """
    Sets the 'text_vec' field in the observation.
    Useful to override to change vectorization behavior
    """
    obs = super().METHOD_NAME(*args, **kwargs)
    if self.opt.get('legacy') and 'text_vec' in obs:
        if obs['text_vec'][0] != self.dict[SOC_TOKEN]:
            soc_tensor = torch.LongTensor([self.dict[SOC_TOKEN]])
            obs.force_set('text_vec', torch.cat([soc_tensor, obs['text_vec']]))
    return obs