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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, primitive=False, sort=False, merge_tol=0.0):
 """ Reads a structure from a string. Args: input_string (str):
 String to parse. fmt (str):
 A format specification. primitive (bool):
 Whether to find a primitive cell. Defaults to False. sort (bool):
 Whether to sort the sites in accordance to the default ordering criteria, i.e., electronegativity. merge_tol (float):
 If this is some positive number, sites that are within merge_tol from each other will be merged. Usually 0.01 should be enough to deal with common numerical issues. Returns: IStructure / Structure """

        from pymatgen.io.cif import CifParser
        from pymatgen.io.vasp import Poscar
        from pymatgen.io.cssr import Cssr
        from pymatgen.io.xcrysden import XSF
        from pymatgen.io.atat import Mcsqs
        fmt = fmt.lower()
        if fmt == "cif":
            parser = CifParser.from_string(input_string)
            s = parser.get_structures(primitive=primitive)[0]
        elif fmt == "poscar":
            s = Poscar.from_string(input_string, False,
                                   read_velocities=False).structure
        elif fmt == "cssr":
            cssr = Cssr.from_string(input_string)
            s = cssr.structure
        elif fmt == "json":
            d = json.loads(input_string)
            s = Structure.from_dict(d)
        elif fmt == "yaml":
            import ruamel.yaml as yaml
            d = yaml.safe_load(input_string)
            s = Structure.from_dict(d)
        elif fmt == "xsf":
            s = XSF.from_string(input_string).structure
        elif fmt == "mcsqs":
            s = Mcsqs.structure_from_string(input_string)
        else:
            raise ValueError("Unrecognized format `%s`!" % fmt)

        if sort:
            s = s.get_sorted_structure()
        if merge_tol:
            s.merge_sites(merge_tol)
        return cls.from_sites(s)