[V1] Update structured output offline inference example

Update this example to work with V1. The grammar specified was not
comaptible with xgrammar. This worked with V0 as we would automatically
fall back to outlines.

In V1 we have fallback support, but you have to opt-in to it by setting
your backend to `auto`. Grammar type support varies among the backends.

Signed-off-by: Russell Bryant <[email protected]>

Author: russellb

examples/offline_inference/structured_outputs.py

@@ -19,7 +19,7 @@
 print(outputs[0].outputs[0].text)
 
 # Guided decoding by Regex
-guided_decoding_params = GuidedDecodingParams(regex="\w+@\w+\.com\n")
+guided_decoding_params = GuidedDecodingParams(regex=r"\w+@\w+\.com\n")
 sampling_params = SamplingParams(guided_decoding=guided_decoding_params,
                                  stop=["\n"])
 prompt = ("Generate an email address for Alan Turing, who works in Enigma."
@@ -57,17 +57,12 @@ class CarDescription(BaseModel):
 
 # Guided decoding by Grammar
 simplified_sql_grammar = """
-    ?start: select_statement
-
-    ?select_statement: "SELECT " column_list " FROM " table_name
-
-    ?column_list: column_name ("," column_name)*
-
-    ?table_name: identifier
-
-    ?column_name: identifier
-
-    ?identifier: /[a-zA-Z_][a-zA-Z0-9_]*/
+root ::= select_statement
+select_statement ::= "SELECT " column " from " table " where " condition
+column ::= "col_1 " | "col_2 "
+table ::= "table_1 " | "table_2 "
+condition ::= column "= " number
+number ::= "1 " | "2 "
 """
 guided_decoding_params = GuidedDecodingParams(grammar=simplified_sql_grammar)
 sampling_params = SamplingParams(guided_decoding=guided_decoding_params)