def METHOD_NAME(x: np.ndarray, A1: float, A2: float, f1: float, f2: float) -> np.ndarray:
    """Return :math:`A_1\\cdot f_1^x+A_2\\cdot f_2^x` where ``x`` is an ``np.ndarray`` and
    ``A1``, ``f1``, ``A2``, ``f2`` are floats. There is no linear offsett B.
    """
    x = np.array(x, dtype=complex)
    return A1 * f1**x + A2 * f2**x