Fix the musicgen example. (#724)

* Fix the musicgen example.

* Retrieve the weights from the hub.

candle-examples/examples/musicgen/main.rs

@@ -16,11 +16,12 @@ mod nn;
 mod t5_model;
 
 use musicgen_model::{GenConfig, MusicgenForConditionalGeneration};
-use nn::VarBuilder;
 
 use anyhow::{Error as E, Result};
 use candle::DType;
+use candle_nn::VarBuilder;
 use clap::Parser;
+use hf_hub::{api::sync::Api, Repo, RepoType};
 
 const DTYPE: DType = DType::F32;
 
@@ -33,11 +34,11 @@ struct Args {
 
     /// The model weight file, in safetensor format.
     #[arg(long)]
-    model: String,
+    model: Option<String>,
 
     /// The tokenizer config.
     #[arg(long)]
-    tokenizer: String,
+    tokenizer: Option<String>,
 }
 
 fn main() -> Result<()> {
@@ -45,10 +46,26 @@ fn main() -> Result<()> {
 
     let args = Args::parse();
     let device = candle_examples::device(args.cpu)?;
-    let mut tokenizer = Tokenizer::from_file(args.tokenizer).map_err(E::msg)?;
+    let tokenizer = match args.tokenizer {
+        Some(tokenizer) => std::path::PathBuf::from(tokenizer),
+        None => Api::new()?
+            .model("facebook/musicgen-small".to_string())
+            .get("tokenizer.json")?,
+    };
+    let mut tokenizer = Tokenizer::from_file(tokenizer).map_err(E::msg)?;
     let _tokenizer = tokenizer.with_padding(None).with_truncation(None);
 
-    let model = unsafe { candle::safetensors::MmapedFile::new(args.model)? };
+    let model = match args.model {
+        Some(model) => std::path::PathBuf::from(model),
+        None => Api::new()?
+            .repo(Repo::with_revision(
+                "facebook/musicgen-small".to_string(),
+                RepoType::Model,
+                "refs/pr/13".to_string(),
+            ))
+            .get("model.safetensors")?,
+    };
+    let model = unsafe { candle::safetensors::MmapedFile::new(model)? };
     let model = model.deserialize()?;
     let vb = VarBuilder::from_safetensors(vec![model], DTYPE, &device);
     let config = GenConfig::small();