Add a couple functions required for yolo. (#527)

candle-core/src/tensor.rs

@@ -487,6 +487,28 @@ impl Tensor {
         self.to_scalar::<S>()
     }
 
+    /// Repeat this tensor along the specified dimensions.
+    pub fn repeat<S: Into<Shape>>(&self, shape: S) -> Result<Tensor> {
+        // Similar to PyTorch, we extend the number of dimensions of self if needed.
+        let repeats = shape.into();
+        let repeats = repeats.dims();
+        let mut inp = if self.rank() < repeats.len() {
+            let mut shape = self.dims().to_vec();
+            while shape.len() < repeats.len() {
+                shape.push(1)
+            }
+            self.reshape(shape)?
+        } else {
+            self.clone()
+        };
+        for (idx, &repeat) in repeats.iter().enumerate() {
+            if repeat > 1 {
+                inp = Tensor::cat(&vec![&inp; repeat], idx)?
+            }
+        }
+        Ok(inp)
+    }
+
     /// This operation multiplies the input tensor by `mul` then adds `add` and return the result.
     /// The input values `mul` and `add` are casted to the appropriate type so some rounding might
     /// be performed.