```json
{
  "no": [
    "no"
  ],
  "yes": [
    "yes"
  ]
}
```

Based on the feature description and the task, it appears that the n_r_ecg_p_08 feature represents the presence or absence of paroxysms of supraventricular tachycardia on an electrocardiogram (ECG) at the time of admission to the hospital. 

The dictionary generated shows that for the target class "no" (patients without chronic heart failure), the possible value for the n_r_ecg_p_08 feature is only "no". Similarly, for the target class "yes" (patients with chronic heart failure), the possible value for the n_r_ecg_p_08 feature is only "yes".