Add example to AngleEmbedding (#1908)

* Update angle.py

Add example in documentation

* Update angle.py

reformat

* Apply suggestions from code review

Co-authored-by: antalszava <antalszava@gmail.com>

* Update changelog-dev.md

Co-authored-by: antalszava <antalszava@gmail.com>

doc/releases/changelog-dev.md

@@ -220,9 +220,12 @@
 * Improves the Developer's Guide Testing document.
   [(#1896)](https://github.com/PennyLaneAI/pennylane/pull/1896)
 
+* Added documentation example for AngleEmbedding.
+  [(#1908)](https://github.com/PennyLaneAI/pennylane/pull/1908)
+
 <h3>Contributors</h3>
 
 This release contains contributions from (in alphabetical order):
 
 Guillermo Alonso-Linaje, Benjamin Cordier, Olivia Di Matteo, Jalani Kanem, Ankit Khandelwal, Shumpei Kobayashi,
-Christina Lee, Alejandro Montanez, Romain Moyard, Maria Schuld, Jay Soni, David Wierichs
+Christina Lee, Alejandro Montanez, Romain Moyard, Maria Schuld, Jay Soni, David Wierichs

pennylane/templates/embeddings/angle.py

@@ -43,6 +43,31 @@ class AngleEmbedding(Operation):
             with :math:`N\leq n`
         wires (Iterable): wires that the template acts on
         rotation (str): type of rotations used
+
+    Example:
+
+        Angle embedding encodes the features by using the specified rotation operation.
+
+        .. code-block:: python
+
+            dev = qml.device('default.qubit', wires=3)
+
+            @qml.qnode(dev)
+            def circuit(feature_vector):
+                qml.AngleEmbedding(features=feature_vector, wires=range(3), rotation='Z')
+                qml.Hadamard(0)
+                return qml.probs(wires=range(3))
+
+            X = [1,2,3]
+
+        Here, we have also used rotation angles :class:`RZ`. If not specified, :class:`RX` is used as default.
+        The resulting circuit is:
+
+        >>> print(qml.draw(circuit)(X))
+            0: ──RZ(1)──H──╭┤ Probs
+            1: ──RZ(2)─────├┤ Probs
+            2: ──RZ(3)─────╰┤ Probs
+
     """
 
     num_wires = AnyWires