code: @Nonnull
    public JSInvocation invoke (@Nullable final IJSExpression aExpr, @Nonnull @Nonempty final String sMethod)
    {
      final JSInvocation aInvocation = new JSInvocation (aExpr, sMethod);
      return addStatement (aInvocation);
    }
docs: Creates an invocation statement and adds it to this block.
  
  @param aExpr
  JExpression evaluating to the class or object upon which the named
  method will be invoked
  @param sMethod
  Name of method to invoke
  @return Newly generated {@link JSInvocation}