Write me the Python code of a command line tool to read a set of DICOM files of PET/CT images from a directory named "inputdirectory" given as a parameter in the command line call, resample them with the slice spacing "slicespacing" and the pixel size "pixelsize", also given as parameters in the command line call. The tool has to write the resampled data into a directory with the name "outputdirectory", also specified as a parameter in the command line call. The resampled PET images must preserve the DICOM tags for SUV calculations. The Unique series Identifier may be changed.