Generates the string representation of the CTRL file. This is
        the mininmal CTRL file necessary to execute lmhart.run.

def get_string(self, sigfigs=8):
        """
        Generates the string representation of the CTRL file. This is
        the mininmal CTRL file necessary to execute lmhart.run.
        """
        ctrl_dict = self.as_dict()
        lines = [] if "HEADER" not in ctrl_dict else \
            ["HEADER".ljust(10) + self.header]
        if "VERS" in ctrl_dict:
            lines.append("VERS".ljust(10) + self.version)

        lines.append("STRUC".ljust(10) +
                     "ALAT="+str(round(ctrl_dict["ALAT"], sigfigs)))
        for l, latt in enumerate(ctrl_dict["PLAT"]):
            if l == 0:
                line = "PLAT=".rjust(15)
            else:
                line = " ".ljust(15)
            line += " ".join([str(round(v, sigfigs)) for v in latt])
            lines.append(line)

        for cat in ["CLASS", "SITE"]:
            for a, atoms in enumerate(ctrl_dict[cat]):
                if a == 0:
                    line = [cat.ljust(9)]
                else:
                    line = [" ".ljust(9)]
                for token, val in sorted(atoms.items()):
                    if token == "POS":
                        line.append("POS=" +
                                    " ".join([str(round(p, sigfigs))
                                              for p in val]))
                    else:
                        line.append(token + "=" + str(val))
                line = " ".join(line)
                lines.append(line)

        return "\n".join(lines)+"\n"