code: def decipher_atom_key(atom_key, forcefield):
      
      load_funcs = {
          'DLF': dlf_notation,
          'DL_F': dlf_notation,
          'OPLS': opls_notation,
          'OPLSAA': opls_notation,
          'OPLS2005': opls_notation,
          'OPLS3': opls_notation,
      }
      if forcefield.upper() in load_funcs.keys():
          return load_funcs[forcefield.upper()](atom_key)
      else:
          raise _ForceFieldError(
              ("Unfortunetely, '{0}' forcefield is not supported by pyWINDOW."
               " For list of supported forcefields see User's Manual or "
               "MolecularSystem._decipher_atom_keys() function doc string."
               ).format(forcefield))
docs: Return element for deciphered atom key.
  
      This functions checks if the forcfield specified by user is supported
      and passes the atom key to the appropriate function for deciphering.
  
      Parameters
      ----------
      atom_key : str
          The atom key which is to be deciphered.
  
      forcefield : str
          The forcefield to which the atom key belongs to.
  
      Returns
      -------
      str
          A string that is the periodic table element equvalent of forcefield
          atom key.