I want to classify the sentiment of text using OpenPrompt.
Create a prompt template for sentiment classification.
The application should:

• Take an input sentence or paragraph
• Classify the sentiment as Positive, Negative, or Neutral
• Use a clear and reusable prompt template
• Make it easy to apply to multiple sentences without retraining
• Include an example input and expected output
• Use only OpenPrompt and a pre-trained language model
• Provide a professional, well-commented Python implementation