docs: def get_isotope_dicts(element='', database='ENDF_VII'):
      """return a dictionary with list of isotopes found in database and name of database files
      
      Parameters:
      ===========
      element: string. Name of the element
        ex: 'Ag'
      database: string (default is ENDF_VII)
      
      Returns:
      ========
      dictionary with isotopes and files 
        ex: {'Ag': {'isotopes': ['107-Ag','109-Ag'],
                    'file_names': ['Ag-107.csv','Ag-109.csv']}}
      
      """
      _file_path = os.path.abspath(os.path.dirname(__file__))
      _database_folder = os.path.join(_file_path, 'reference_data', database)
      _element_search_path = os.path.join(_database_folder, element + '-*.csv')
  
      list_files = glob.glob(_element_search_path)
      if not list_files:
          raise ValueError("File names contains NO '-', the name should in the format of 'Cd-115_m1' or 'Cd-114'")
      list_files.sort()
      isotope_dict = {'isotopes': {'list': [],
                                   'file_names': [],
                                   'density': {'value': np.NaN,
                                               'units': 'g/cm3'},
                                   'mass': {'value': [],
                                            'units': 'g/mol',
                                            },
                                   'isotopic_ratio': [], },
                      'density': {'value': np.NaN,
                                  'units': 'g/cm3'},
                      'molar_mass': {'value': np.NaN,
                                     'units': 'g/mol'},
                      }
  
      # isotope_dict_mirror = {}
      _isotopes_list = []
      _isotopes_list_files = []
      _isotopes_mass = []
      _isotopes_density = []
      _isotopes_atomic_ratio = []
      _density = np.NaN
      _molar_mass = np.NaN
  
      for file in list_files:
          # Obtain element, z number from the basename
          _basename = os.path.basename(file)
          filename = os.path.splitext(_basename)[0]
          if '-' in filename:
              [_name, _number] = filename.split('-')
              if '_' in _number:
                  [aaa, meta] = _number.split('_')
                  _number = aaa[:]
          else:
              _split_list = re.split(r'(\d+)', filename)
              if len(_split_list) == 2:
                  [_name, _number] = _split_list
              else:
                  _name = _split_list[0]
                  _number = _split_list[1]
          if _number == '0':
              _number = '12'
          _symbol = _number + '-' + _name
          isotope = str(_symbol)
  
          _isotopes_list.append(isotope)
          _isotopes_list_files.append(_basename)
          _isotopes_mass.append(get_mass(isotope))
          _isotopes_atomic_ratio.append(get_abundance(isotope))
          _isotopes_density.append(get_density(isotope))
          _density = get_density(element)
          _molar_mass = get_mass(element)
  
      isotope_dict['isotopes']['list'] = _isotopes_list
      isotope_dict['isotopes']['file_names'] = _isotopes_list_files
      isotope_dict['isotopes']['mass']['value'] = _isotopes_mass
      isotope_dict['isotopes']['isotopic_ratio'] = _isotopes_atomic_ratio
      isotope_dict['isotopes']['density']['value'] = _isotopes_density
      isotope_dict['density']['value'] = _density
      isotope_dict['molar_mass']['value'] = _molar_mass
      return isotope_dict