Add BindingsArray as allowed input type to BindingsArray.coerce()

qiskit/primitives/containers/bindings_array.py

@@ -270,6 +270,8 @@ def coerce(cls, bindings_array: BindingsArrayLike) -> BindingsArray:
             bindings_array = cls(bindings_array)
         elif isinstance(bindings_array, Mapping):
             bindings_array = cls(kwvals=bindings_array)
+        elif isinstance(bindings_array, BindingsArray):
+            return bindings_array
         else:
             raise TypeError(f"Unsupported type {type(bindings_array)} is given.")
         return bindings_array

test/python/primitives/containers/test_bindings_array.py

@@ -431,3 +431,20 @@ def test_simple_vals(self):
             self.assertEqual(ba.shape, (1,))
             self.assertEqual(len(ba.vals), 1)
             np.testing.assert_allclose(ba.vals[0], [[1, 2, 3]])
+
+    def test_coerce(self):
+        """Test the coerce() method."""
+        # BindingsArray passthrough
+        arg = BindingsArray({"a": np.linspace(0, 1, 5)})
+        ba = BindingsArray.coerce(arg)
+        self.assertEqual(ba, arg)
+
+        # dict-valued input
+        arg = {"a": np.linspace(0, 1, 5)}
+        ba = BindingsArray.coerce(arg)
+        self.assertEqual(ba.num_parameters, 1)
+
+        # None-valued input
+        arg = None
+        ba = BindingsArray.coerce(None)
+        self.assertEqual(ba.num_parameters, 0)