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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 parse(self, ddl=None, source_database=None):
 """ Parse DDL script. :param ddl: DDL script :return: DdlParseTable, Parsed table define info. """


        if ddl is not None:
            self._ddl = ddl

        if source_database is not None:
            self.source_database = source_database

        if self._ddl is None:
            raise ValueError("DDL is not specified")

        ret = self._DDL_PARSE_EXPR.parseString(self._ddl)
        # print(ret.dump())

        if "schema" in ret:
            self._table.schema = ret["schema"]

        self._table.name = ret["table"]
        self._table.is_temp = True if "temp" in ret else False

        for ret_col in ret["columns"]:

            if ret_col.getName() == "column":
                # add column
                col = self._table.columns.append(
                    column_name=ret_col["name"],
                    data_type_array=ret_col["type"],
                    array_brackets=ret_col['array_brackets'] if "array_brackets" in ret_col else None)

                if "constraint" in ret_col:
                    col.constraint = ret_col["constraint"]

            elif ret_col.getName() == "constraint":
                # set column constraint
                for col_name in ret_col["constraint_columns"]:
                    col = self._table.columns[col_name]

                    if ret_col["type"] == "PRIMARY KEY":
                        col.not_null = True
                        col.primary_key = True
                    elif ret_col["type"] in ["UNIQUE", "UNIQUE KEY"]:
                        col.unique = True
                    elif ret_col["type"] == "NOT NULL":
                        col.not_null = True

        return self._table