def perturb_field(vector_field, perturbation):
    """
    Returns the vector field function with a linearly added pertubation
    Both input function should input (t, u), with t: float, and u: ndarray
    Also, the output of these funcs must be ndarrays of the same shape
    
    Parameters
    ----------
        vector_field: function
            unperturbed vector field
    
        perturbation: function
            forcing added to the vector field
    
    Returns
    -------
        perturbed function
    """
    return lambda t, u: vector_field(t, u) + perturbation(t, u)