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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 to_string(self, format="smi", dialect=None, with_header=False, fragment_id=None, constraints=None):
 r""" Produce a string representation of the molecule. This function wraps and extends the functionality of OpenBabel (which is accessible through `to_pybel`). Many chemical formats can thus be output (see the `pybel.outformats` variable for a list of available output formats). Parameters format : `str`, optional Chemical file format of the returned string representation (see examples below). dialect : `str`, optional Format dialect. This encompasses enhancements provided for some subformats. If ``"standard"`` or `None`, the output provided by OpenBabel is used with no or minimal modification. See notes below. with_header : `bool`, optional If `format` encompasses a header, allow it in the returned string. This would be, for instance, the first two lines of data for ``format="xyz"`` (see examples below). This might not work with all dialects and/or formats. fragment_id : `str`, optional Indentify molecular fragments (see examples below). This might not work with all dialects and/or formats. constraints : iterable object of `int` Set cartesian constraints for selected atoms (see examples below). This might not work with all dialects and/or formats. Returns ------- `str` String representation of molecule in the specified format and/or dialect. Raises ------ KeyError Raised if `dialect` value is currently not supported or if `fragment_id` is given with a currently not supported `dialect` value. Notes ----- Format dialects are subformats that support extended functionality. Currently supported dialects are: - for ``format="xyz"``: - ``"ADF"``, ``"ORCA"``. Examples -------- By default, a SMILES string is returned: 'O=O\tdioxygen' Cartesian coordinates can be produced with ``format="xyz"``, which is equivalent to printing an `Atoms` instance: O 0.00000 0.00000 0.00000 O 0.00000 0.00000 1.21000 O 0.00000 0.00000 0.00000 O 0.00000 0.00000 1.21000 Header lines are disabled by default (for ``format="xyz"``, for example, the header stores the number of atoms in the molecule and a comment or title line), but this can be reversed with ``with_header=True``: 2 dioxygen O 0.00000 0.00000 0.00000 O 0.00000 0.00000 1.21000 Coordinates for packages such as GAMESS and MOPAC are also supported: O 8.0 -1.6289300000 -0.0413800000 0.3713700000 H 1.0 -0.6980300000 -0.0916800000 0.0933700000 H 1.0 -2.0666300000 -0.7349800000 -0.1366300000 O 8.0 1.2145700000 0.0317200000 -0.2762300000 H 1.0 1.4492700000 0.9167200000 -0.5857300000 H 1.0 1.7297700000 -0.0803800000 0.5338700000 O -1.62893 1 -0.04138 1 0.37137 1 H -0.69803 1 -0.09168 1 0.09337 1 H -2.06663 1 -0.73498 1 -0.13663 1 O 1.21457 1 0.03172 1 -0.27623 1 H 1.44927 1 0.91672 1 -0.58573 1 H 1.72977 1 -0.08038 1 0.53387 1 Constraining of cartesian coordinates works with MOPAC format: O -1.62893 0 -0.04138 0 0.37137 0 H -0.69803 1 -0.09168 1 0.09337 1 H -2.06663 1 -0.73498 1 -0.13663 1 O 1.21457 0 0.03172 0 -0.27623 0 H 1.44927 1 0.91672 1 -0.58573 1 H 1.72977 1 -0.08038 1 0.53387 1 Fragment identification is supported for ``"ADF"`` and ``"ORCA"`` dialects: O -1.62893 -0.04138 0.37137 f=dimer H -0.69803 -0.09168 0.09337 f=dimer H -2.06663 -0.73498 -0.13663 f=dimer O 1.21457 0.03172 -0.27623 f=dimer H 1.44927 0.91672 -0.58573 f=dimer H 1.72977 -0.08038 0.53387 f=dimer O(1) -1.62893 -0.04138 0.37137 H(1) -0.69803 -0.09168 0.09337 H(1) -2.06663 -0.73498 -0.13663 O(1) 1.21457 0.03172 -0.27623 H(1) 1.44927 0.91672 -0.58573 H(1) 1.72977 -0.08038 0.53387 """

        s = self.to_pybel().write(format).strip()

        if dialect is None:
            dialect = "standard"
        dialect = dialect.lower()

        if format == "xyz":
            natom, comment, body = s.split("\n", 2)

            if dialect in {"adf", "orca", "standard"}:
                if fragment_id is not None:
                    if dialect == "adf":
                        body = \
                            "\n".join(["{}       f={}".format(line,
                                                              fragment_id)
                                       for line in body.split("\n")])
                    elif dialect == "orca":
                        fragment_id = "({})".format(fragment_id)
                        body = \
                            "\n".join([line.replace(" " * len(fragment_id),
                                                    fragment_id, 1)
                                       for line in body.split("\n")])
                    else:
                        raise KeyError("fragment_id currently not supported "
                                       "with dialect '{}'".format(dialect))
            else:
                raise KeyError("dialect '{}' currently not "
                               "supported".format(dialect))

            if with_header:
                s = "\n".join([natom, comment, body])
            else:
                s = body

        elif format == "gamin":
            lines = s.split("\n")
            begin = "\n".join([line.strip() for line in lines[:5]])
            body = "\n".join([line.strip() for line in lines[5:-1]])

            if with_header:
                s = "\n".join([begin, body])
            else:
                s = body

        elif format == "mop":
            chunks = s.split("\n", 2)
            begin = "\n".join([line.strip() for line in chunks[:2]])
            body = chunks[2].strip()

            if constraints is not None:
                body = body.split("\n")
                for i in constraints:
                    body[i] = _re.sub(' 1( |$)', ' 0\g<1>', body[i])
                body = "\n".join(body)

            if with_header:
                s = "\n".join([begin, body])
            else:
                s = body

        return s.strip()