def fft_coefficient(self, x, param=None):
        """
        As in tsfresh `fft_coefficient <https://github.com/blue-yonder/tsfresh/blob/master/tsfresh/feature_extraction/\
        feature_calculators.py#L852>`_ \
        Calculates the fourier coefficients of the one-dimensional discrete Fourier Transform for real input by fast \
        fourier transformation algorithm
        
        
        .. math:: 
        
            A_k =  \\sum_{m=0}^{n-1} a_m \\exp \\left \\{ -2 \\pi i \\frac{m k}{n} \\right \\}, \\qquad k = 0, \\ldots , n-1.


        The resulting coefficients will be complex, this feature calculator can return the real part (attr=="real"), \
        the imaginary part (attr=="imag), the absolute value (attr=""abs) and the angle in degrees (attr=="angle).
        
        :param x: the time series to calculate the feature of
        :type x: pandas.Series
        :param param: contains dictionaries {"coeff": x, "attr": s} with x int and x >= 0, s str and in ["real", "imag"\
        , "abs", "angle"]
        :type param: list
        :return: the different feature values
        :rtype: pandas.Series
        """
        if param is None:
            param = [{'attr': 'abs', 'coeff': 44}, {'attr': 'abs', 'coeff': 63}, {'attr': 'abs', 'coeff': 0},
                     {'attr': 'real', 'coeff': 0}, {'attr': 'real', 'coeff': 23}]
        _fft_coef = feature_calculators.fft_coefficient(x, param)
        logging.debug("fft coefficient by tsfresh calculated")
        return list(_fft_coef)
As in tsfresh `fft_coefficient <https://github.com/blue-yonder/tsfresh/blob/master/tsfresh/feature_extraction/\
        feature_calculators.py#L852>`_ \
        Calculates the fourier coefficients of the one-dimensional discrete Fourier Transform for real input by fast \
        fourier transformation algorithm
        
        
        .. math:: 
        
            A_k =  \\sum_{m=0}^{n-1} a_m \\exp \\left \\{ -2 \\pi i \\frac{m k}{n} \\right \\}, \\qquad k = 0, \\ldots , n-1.


        The resulting coefficients will be complex, this feature calculator can return the real part (attr=="real"), \
        the imaginary part (attr=="imag), the absolute value (attr=""abs) and the angle in degrees (attr=="angle).
        
        :param x: the time series to calculate the feature of
        :type x: pandas.Series
        :param param: contains dictionaries {"coeff": x, "attr": s} with x int and x >= 0, s str and in ["real", "imag"\
        , "abs", "angle"]
        :type param: list
        :return: the different feature values
        :rtype: pandas.Series