add usage guide and init

recipes/use_cases/prompt-migration/examples/usage.py

@@ -0,0 +1,37 @@
+import dspy
+from prompt_migration.engine import PromptMigrationEngine, PromptTemplate
+from prompt_migration.evaluator import PromptEvaluator
+
+# Initialize LMs
+openai_lm = dspy.OpenAI(model="gpt-3.5-turbo")
+target_lm = dspy.HFModel(model="gpt2")
+
+# Create migration engine
+engine = PromptMigrationEngine(openai_lm, target_lm)
+
+# Define source prompt
+source_prompt = PromptTemplate(
+    template="Summarize the following text: {text}",
+    input_variables=["text"],
+    model_type="openai"
+)
+
+# Example evaluation dataset
+eval_dataset = [
+    {"text": "Example text 1", "expected_summary": "Summary 1"},
+    {"text": "Example text 2", "expected_summary": "Summary 2"},
+]
+
+# Migrate prompt
+migrated_prompt = engine.migrate_prompt(source_prompt, eval_dataset)
+
+# Evaluate migration
+evaluator = PromptEvaluator(openai_lm, target_lm)
+metrics = evaluator.evaluate(
+    source_prompt.template,
+    migrated_prompt.template,
+    eval_dataset
+)
+
+print(f"Migrated prompt: {migrated_prompt.template}")
+print(f"Evaluation metrics: {metrics}")