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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def from_str(cls, input_string, fmt):
 """ Reads the molecule from a string. Args: input_string (str):
 String to parse. fmt (str):
 Format to output to. Defaults to JSON unless filename is provided. If fmt is specifies, it overrides whatever the filename is. Options include "xyz", "gjf", "g03", "json". If you have OpenBabel installed, any of the formats supported by OpenBabel. Non-case sensitive. Returns: IMolecule or Molecule. """

        from pymatgen.io.xyz import XYZ
        from pymatgen.io.gaussian import GaussianInput
        if fmt.lower() == "xyz":
            m = XYZ.from_string(input_string).molecule
        elif fmt in ["gjf", "g03", "g09", "com", "inp"]:
            m = GaussianInput.from_string(input_string).molecule
        elif fmt == "json":
            d = json.loads(input_string)
            return cls.from_dict(d)
        elif fmt == "yaml":
            import ruamel.yaml as yaml
            d = yaml.safe_load(input_string)
            return cls.from_dict(d)
        else:
            from pymatgen.io.babel import BabelMolAdaptor
            m = BabelMolAdaptor.from_string(input_string,
                                            file_format=fmt).pymatgen_mol
        return cls.from_sites(m)