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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_sql(self, url, table_name, *, schema=None, fields=None, fields_to_explode=None, if_exists="fail", dtype=None):
 """ Export items as rows in a PostgreSQL table. Parameters url: string Connection string to connect to the database. Example: "postgresql://postgres@127.0.0.1:5432/testdb" table_name: string Name of the database table. Note that if this name contains a dot ('.') and `schema` is not specified, the first part of the name before the dot will be interpreted as the schema name. schema : string, optional Specify the schema (if database flavor supports this). If None, use default schema or derive the schema name from `table_name`. fields: list or dict List of field names to export, or dictionary mapping output column names to attribute names of the generators. Examples: fields=['field_name_1', 'field_name_2'] fields={'COL1': 'field_name_1', 'COL2': 'field_name_2'} fields_to_explode: list or None Optional list of field names where each entry (which must itself be a sequence) is to be "exploded" into separate rows. if_exists : {'fail', 'do_nothing', 'replace', 'append'}, default 'fail' - fail: If table exists, raise an error. - do_nothing: If table exists, do nothing and immediately return. - replace: If table exists, drop it, recreate it, and insert data. - append: If table exists, insert data. Create if does not exist. dtype : dict, optional Specifying the datatype for columns. The keys should be the column names and the values should be the SQLAlchemy types or strings for the sqlite3 legacy mode. This is passed through to pandas.DataFrame.to_sql(). """

        if schema is None:
            schema, table_name = _extract_schema_if_given(table_name)

        engine = create_engine(url)
        ins = inspect(engine)

        if schema is not None and schema not in ins.get_schema_names():
            logger.debug(f"Creating non-existing schema: '{schema}'")
            engine.execute(CreateSchema(schema))

        if table_name in ins.get_table_names(schema=schema) and if_exists == 'do_nothing':
            logger.debug("Table already exists (use if_exists='replace' or if_exists='append' to modify it).")
            return

        if if_exists == 'do_nothing':
            # we handled the 'do nothing' case above; change to an option that pandas will understand
            if_exists = 'fail'

        with engine.begin() as conn:
            self.to_df(fields=fields, fields_to_explode=fields_to_explode).to_sql(
                table_name, conn, schema=schema, index=False, if_exists=if_exists, dtype=dtype)