How to use the agate.Table.from_json function in agate

def test_from_json_error_newline_key(self):
        with self.assertRaises(ValueError):
            table = Table.from_json('examples/test.json', newline=True, key='test')  # noqa

def test_from_json_file_like_object(self):
        table1 = Table(self.rows, self.column_names, self.column_types)

        with open('examples/test.json') as f:
            table2 = Table.from_json(f)

        self.assertColumnNames(table2, self.column_names)
        self.assertColumnTypes(table2, [Number, Text, Boolean, Date, DateTime, TimeDelta])
        self.assertRows(table2, table1.rows)

def test_from_json_file_like_object(self):
        table1 = Table(self.rows, self.column_names, self.column_types)

        with open('examples/test.json') as f:
            table2 = Table.from_json(f)

        self.assertColumnNames(table2, self.column_names)
        self.assertColumnTypes(table2, [Number, Text, Boolean, Date, DateTime, TimeDelta])
        self.assertRows(table2, table1.rows)

def test_from_json_with_key(self):
        table1 = Table(self.rows, self.column_names, self.column_types)
        table2 = Table.from_json('examples/test_key.json', key='data')

        self.assertColumnNames(table2, self.column_names)
        self.assertColumnTypes(table2, [Number, Text, Boolean, Date, DateTime, TimeDelta])
        self.assertRows(table2, table1.rows)

def test_from_json_nested(self):
        table = Table.from_json('examples/test_nested.json')

        self.assertColumnNames(table, ['one', 'two/two_a', 'two/two_b', 'three/0', 'three/1', 'three/2'])
        self.assertColumnTypes(table, [Number, Text, Text, Text, Number, Text])
        self.assertRows(table, [
            [1, 'a', 'b', 'a', 2, 'c'],
            [2, 'c', 'd', 'd', 2, 'f']
        ])

def test_from_json_mixed_keys(self):
        table = Table.from_json('examples/test_mixed.json')

        self.assertColumnNames(table, ['one', 'two', 'three', 'four', 'five'])
        self.assertColumnTypes(table, [Number, Number, Text, Text, Number])
        self.assertRows(table, [
            [1, 4, 'a', None, None],
            [2, 3, 'b', 'd', None],
            [None, 2, u'👍', None, 5]
        ])

def test_from_json_no_type_tester(self):
        tester = TypeTester(limit=0)

        table = Table.from_json('examples/test.json', column_types=tester)

        self.assertColumnTypes(table, [Text, Text, Text, Text, Text, Text])

def test_from_json_mixed_keys(self):
        table = Table.from_json('examples/test_mixed.json')

        self.assertColumnNames(table, ['one', 'two', 'three', 'four', 'five'])
        self.assertColumnTypes(table, [Number, Number, Text, Text, Number])
        self.assertRows(table, [
            [1, 4, 'a', None, None],
            [2, 3, 'b', 'd', None],
            [None, 2, u'👍', None, 5]
        ])

# Convert the file.
        if filetype == 'csv' and self.args.no_inference and not self.args.no_header_row and not self.args.skip_lines and self.args.sniff_limit == 0:
            reader = agate.csv.reader(self.input_file, **self.reader_kwargs)
            writer = agate.csv.writer(self.output_file, **self.writer_kwargs)
            writer.writerows(reader)
        elif filetype == 'fixed':
            self.output_file.write(fixed2csv(self.input_file, schema, output=self.output_file, **kwargs))
        elif filetype == 'geojson':
            self.output_file.write(geojson2csv(self.input_file, **kwargs))
        elif filetype in ('csv', 'dbf', 'json', 'ndjson', 'xls', 'xlsx'):
            if filetype == 'csv':
                table = agate.Table.from_csv(self.input_file, **kwargs)
            elif filetype == 'json':
                table = agate.Table.from_json(self.input_file, key=self.args.key, **kwargs)
            elif filetype == 'ndjson':
                table = agate.Table.from_json(self.input_file, key=self.args.key, newline=True, **kwargs)
            elif filetype == 'xls':
                table = agate.Table.from_xls(self.input_file, sheet=self.args.sheet, encoding_override=self.args.encoding_xls, **kwargs)
            elif filetype == 'xlsx':
                table = agate.Table.from_xlsx(self.input_file, sheet=self.args.sheet, **kwargs)
            elif filetype == 'dbf':
                if not hasattr(self.input_file, 'name'):
                    raise ValueError('DBF files can not be converted from stdin. You must pass a filename.')
                table = agate.Table.from_dbf(self.input_file.name, **kwargs)
            table.to_csv(self.output_file, **self.writer_kwargs)

        if self.args.write_sheets:
            # Close and re-open the file, as the file object has been mutated or closed.
            self.input_file.close()

            self.input_file = self.open_excel_input_file(path)

"""
    Convert a file of a specified format to CSV.
    """
    if format == 'fixed':
        if not schema:
            raise ValueError('schema must not be null when format is "fixed"')
        output.write(fixed2csv(f, schema, output=output, **kwargs))
    elif format == 'geojson':
        output.write(geojson2csv(f, **kwargs))
    elif format in ('csv', 'dbf', 'json', 'ndjson', 'xls', 'xlsx'):
        if format == 'csv':
            table = agate.Table.from_csv(f, **kwargs)
        elif format == 'json':
            table = agate.Table.from_json(f, key=key, **kwargs)
        elif format == 'ndjson':
            table = agate.Table.from_json(f, key=key, newline=True, **kwargs)
        elif format == 'xls':
            table = agate.Table.from_xls(f, sheet=kwargs.get('sheet', None))
        elif format == 'xlsx':
            table = agate.Table.from_xlsx(f, sheet=kwargs.get('sheet', None))
        elif format == 'dbf':
            with dbf.Table(f.name) as db:
                column_names = db.field_names
                table = agate.Table(db, column_names)
        table.to_csv(output)
    else:
        raise ValueError('format "%s" is not supported' % format)