Download the pre-computed sketch of the RefSeq database, and compress it with gzip
        :param databasepath: path to use to save the database

def mash(self, databasepath):
        """
        Download the pre-computed sketch of the RefSeq database, and compress it with gzip
        :param databasepath: path to use to save the database
        """
        logging.info('Downloading pre-computed RefSeq MASH sketches')
        # Create the folder in which the database is to be stored
        databasepath = self.create_database_folder(databasepath=databasepath,
                                                   database='mash')
        output_file = os.path.join(databasepath, 'assembly_summary_refseq.txt')
        # Download the assembly summary RefSeq document
        if not os.path.isfile(output_file):
            self.database_download(output_file=output_file,
                                   database_path=databasepath,
                                   target_url='ftp://ftp.ncbi.nih.gov/genomes/ASSEMBLY_REPORTS/'
                                              'assembly_summary_refseq.txt'
                                   )
        # Set the call to create the database
        output_file = os.path.join(databasepath, 'RefSeqSketchesDefaults.msh')
        # Download the database
        if not os.path.isfile(output_file):
            self.database_download(output_file=output_file,
                                   database_path=databasepath,
                                   target_url='https://gembox.cbcb.umd.edu/mash/refseq.genomes.k21s1000.msh',
                                   complete=True)