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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 add(self, cell, overwrite_duplicate=False):
 """ Add one or more cells to the library. Parameters cell : ``Cell`` of list of ``Cell`` Cells to be included in the library. overwrite_duplicate : bool If True an existing cell with the same name in the library will be overwritten. Returns ------- out : ``GdsLibrary`` This object. """

        if isinstance(cell, Cell):
            if (not overwrite_duplicate and cell.name in self.cell_dict and
                    self.cell_dict[cell.name] is not cell):
                raise ValueError("[GDSPY] cell named {0} already present in "
                                 "library.".format(cell.name))
            self.cell_dict[cell.name] = cell
        else:
            for c in cell:
                if (not overwrite_duplicate and c.name in self.cell_dict and
                        self.cell_dict[c.name] is not c):
                    raise ValueError("[GDSPY] cell named {0} already present "
                                     "in library.".format(c.name))
                self.cell_dict[c.name] = c
        return self