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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_poscar_string(poscar_string, transformations=None):
 """ Generates TransformedStructure from a poscar string. Args: poscar_string (str):
 Input POSCAR string. transformations ([Transformations]):
 Sequence of transformations to be applied to the input structure. """

        p = Poscar.from_string(poscar_string)
        if not p.true_names:
            raise ValueError("Transformation can be craeted only from POSCAR "
                             "strings with proper VASP5 element symbols.")
        raw_string = re.sub(r"'", "\"", poscar_string)
        s = p.structure
        source_info = {"source": "POSCAR",
                       "datetime": str(datetime.datetime.now()),
                       "original_file": raw_string}
        return TransformedStructure(s, transformations, history=[source_info])