def derivative(f, x, epsilon = 1e-10):
    """
    Calculate derivative of f at x

    ...

    Parameters
    ---
    f : Function to calculate derivative for
    x : Value at which to calculate derivative
    epsilon(optional): Adjustable precision

    Returns
    ---
    value: Derivative of f at x
    """

    x_ = x + epsilon
    value = (f(x_) - f(x)) / epsilon

    return value