docs: def get_calculator_impstr(calculator_name):
      """
      Returns the import string for the calculator
      """
      if calculator_name.lower() == "gpaw" or calculator_name is None:
          return "from gpaw import GPAW as custom_calculator"
      elif calculator_name.lower() == "espresso":
          return "from espresso import espresso as custom_calculator"
      else:
          possibilities = {"abinit":"abinit.Abinit",
                           "aims":"aims.Aims",
                           "ase_qmmm_manyqm":"AseQmmmManyqm",
                           "castep":"Castep",
                           "dacapo":"Dacapo",
                           "dftb":"Dftb",
                           "eam":"EAM",
                           "elk":"ELK",
                           "emt":"EMT",
                           "exciting":"Exciting",
                           "fleur":"FLEUR",
                           "gaussian":"Gaussian",
                           "gromacs":"Gromacs",
                           "mopac":"Mopac",
                           "morse":"MorsePotential",
                           "nwchem":"NWChem",
                           'siesta':"Siesta",
                           "tip3p":"TIP3P",
                           "turbomole":"Turbomole",
                           "vasp":"Vasp",
                           }
          
          current_val = possibilities.get(calculator_name.lower())
          
          package, class_name = (calculator_name,current_val) if current_val else calculator_name.rsplit('.',1)
          
          return "from ase.calculators.{} import {} as custom_calculator".format(package, class_name)