I'm trying to analyse an asymmetric FIR filter with complex coefficients. I know I can use the numpy function freqz to analyse the frequency response of an FIR or IIR-filter with real coefficients. At the moment I'm just using a regular FFT of the FIR filter and I use fftshift to put the negative frequencies in front of 0 and then I do fftfreqs to calculate the frequency bins and finally, I add the carrier frequency to all the frequencies in the array which is given by fftfreqs. Anyway, I'm pretty sure that that's the wrong way.
Never mind, it is absolutely possible to pass a set of complex coefficients to freqz, I got confused because I tried to plot the response without specifying I wanted the absolute value of h, which rendered the warning: 
ComplexWarning: Casting complex values to real discards the imaginary part. Trap for young players like myself!
How to use freqz to get response of complex FIR filter