fix: require Sync for custom errors

src/error.rs

@@ -247,7 +247,7 @@ pub enum Error {
 	#[error("Failed to get operator output: {0}")]
 	GetOperatorOutput(ErrorInternal),
 	#[error("{0}")]
-	CustomError(#[from] Box<dyn std::error::Error + Send>),
+	CustomError(#[from] Box<dyn std::error::Error + Send + Sync + 'static>),
 	#[error("String tensors cannot be borrowed as mutable")]
 	StringTensorNotMutable
 }