@classmethod
def gettype(cls, rng):
    """Get the class for the input file type.

        Now ReacNetGen support the following files:
        LAMMPS bond files: http://lammps.sandia.gov/doc/fix_reax_bonds.html
        LAMMPS dump files: https://lammps.sandia.gov/doc/dump.html
        """
    if rng.inputfiletype not in cls.subclasses:
        raise ValueError(f'Unsupported input file type {rng.inputfiletype}')
    return cls.subclasses[rng.inputfiletype](rng)
