code: def create_map_from_file(self, data_filename):
          
          
          op_filename = data_filename + '.rule'
          
          dataset = mod_datatable.DataTable(data_filename, ',')
          dataset.load_to_array()
          l_map = self.generate_map_from_dataset(dataset)
          with open(op_filename, 'w') as f:
              f.write('# rules file autogenerated by mapper.py v0.1\n')
              f.write('filename:source=' + data_filename + '\n')
              f.write('filename:rule=' + op_filename + '\n\n')
              for row in l_map:
                  #print('ROW = ' , row)
                  if type(row) is str:
                      f.write(row + '\n')
                  else:
                      for v in row:
                          f.write(v)
docs: reads the data_filename into a matrix and calls the main
          function '' to generate a  .rule file based on the data in the map
          
          For all datafiles mapped, there exists a .rule file to define it