Download the UniVec core database
        :param databasepath: path to use to save the database

def univec(self, databasepath):
        """
        Download the UniVec core database
        :param databasepath: path to use to save the database
        """
        logging.info('Downloading univec database')
        databasepath = self.create_database_folder(databasepath, 'univec')
        # Set the name of the output file
        outputfile = os.path.join(databasepath, 'UniVec_core.tfa')
        target_url = 'ftp://ftp.ncbi.nlm.nih.gov/pub/UniVec/UniVec_Core'
        self.database_download(output_file=outputfile,
                               target_url=target_url,
                               database_path=databasepath)
        # Create a copy of the file with a .fasta extension
        if os.path.isfile(outputfile):
            renamed = os.path.splitext(outputfile)[0] + '.fasta'
            shutil.copy(outputfile, renamed)