Why won't the DrawGizmo attribute work in the editor

Every time it is called it gives me this error. It was my assumption that this would allow me to draw Gizmos outside of the OnDrawGizmos function.

 UnityException: Gizmo drawing functions can only be used in OnDrawGizmos and OnDrawGizmosSelected.
 UnityEngine.Gizmos.DrawCube (Vector3 center, Vector3 size) (at C:/buildslave/unity/build/artifacts/generated/common/runtime/GizmoBindings.gen.cs:59)
 VertexM.ExampleGizmo (Vector3 vec, .MeshSaver saver, GizmoType gizmoType) (at Assets/Editor/VertexM.cs:48)
 VertexM.OnSceneGUI () (at Assets/Editor/VertexM.cs:34)
 System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)
 Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
 System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:232)
 System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MethodBase.cs:115)
 UnityEditor.SceneView.CallOnSceneGUI () (at C:/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:2408)
 UnityEditor.SceneView.HandleSelectionAndOnSceneGUI () (at C:/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:1737)
 UnityEditor.SceneView.OnGUI () (at C:/buildslave/unity/build/Editor/Mono/SceneView/SceneView.cs:1569)
 System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)
 Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
 System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:232)
 System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MethodBase.cs:115)
 UnityEditor.HostView.Invoke (System.String methodName, System.Object obj) (at C:/buildslave/unity/build/Editor/Mono/HostView.cs:272)
 UnityEditor.HostView.Invoke (System.String methodName) (at C:/buildslave/unity/build/Editor/Mono/HostView.cs:265)
 UnityEditor.HostView.InvokeOnGUI (Rect onGUIPosition) (at C:/buildslave/unity/build/Editor/Mono/HostView.cs:232)
 UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)
 

Here is the function I am using in the editor.

  [DrawGizmo(GizmoType.NotInSelectionHierarchy | GizmoType.Pickable | GizmoType.Selected)]
    static void ExampleGizmo(Vector3 vec, MeshSaver saver, GizmoType gizmoType)
     {
 
         bool selected = (gizmoType & GizmoType.Selected) > 0;
         Color col = new Color(0.0f, 0.7f, 1f, 1.0f);
         col.a = selected ? 0.5f : 0.2f;
         Gizmos.color = col;
         Gizmos.DrawCube(vec, Vector3.one * 0.1f);
 
     }