def METHOD_NAME(self):
    # initialising with index out of order
    Kzeta = 4
    input_variables_list = [InputVariable('zeta', size=3 * Kzeta, index=0),
                            InputVariable('zeta_dot', size=3 * Kzeta, index=1),  # this should be one
                            InputVariable('u_gust', size=3 * Kzeta, index=2)]
    self.input_variables = LinearVector(input_variables_list)