code: def parse_command_line_parameters():
      
      usage = 'usage: %prog [options] fasta_filepath'
      version = 'Version: %prog 0.1'
      parser = OptionParser(usage=usage, version=version)
  
      # A binary 'verbose' flag
      parser.add_option('-p', '--is_protein', action='store_true',
                        dest='is_protein', default=False,
                        help='Pass if building db of protein sequences [default:'
                             ' False, nucleotide db]')
  
      parser.add_option('-o', '--output_dir', action='store', type='string',
                        dest='output_dir', default=None,
                        help='the output directory [default: directory '
                             'containing input fasta_filepath]')
  
      opts, args = parser.parse_args()
      num_args = 1
      if len(args) != num_args:
          parser.error('Must provide single filepath to build database from.')
  
      return opts, args
docs: Parses command line arguments