Use this widget by including::

    <field name="field_text_json" widget="json_graph" />

For example::

    <field name="values_data" widget="json_graph"/>

The JSON needs to be like::

    fields = ['field1', 'field2', 'field3', ...]
    field_x = 'field_x'
    dictionary = self.value_ids.sorted(field_x).read(fields)
    color = {
        'field1': HEXCOLOR1,
        'field2': '#FFBB78',
        'field3': '#1F77B4',
        ...
    }
    dictionary = self.value_ids.sorted(field_x).read(fields)
    content = {}
    data = []
    for field in fields:
        if field != field_x:
            content[field] = []
            for rec in dictionary:
                content[field].append({'x': rec[field_x], 'y': rec[field]})
            if field in color:
                data.append({'values': content[field], 'key': field,
                    'color': color[field]})
                continue
            data.append({'values': content[field], 'key': field})
    info = {
        'label_x': 'X Label',
        'label_y': 'Y label',
        'data': data
    }
    self.field_text_json = json.dumps(info)

For example::

    fields = ['sequence', 'value', 'sma', 'cma']
    field_x = 'sequence'
    dictionary = self.value_ids.sorted(field_x).read(fields)
    color = {
        'value': '#2CA02C',
        'sma': '#FFBB78'
    }
    dictionary = self.value_ids.sorted(field_x).read(fields)
    content = {}
    data = []
    for field in fields:
        if field != field_x:
            content[field] = []
            for rec in dictionary:
                content[field].append({'x': rec[field_x], 'y': rec[field]})
            if field in color:
                data.append({'values': content[field], 'key': field,
                    'color': color[field]})
                continue
            data.append({'values': content[field], 'key': field})
    info = {
        'label_x': 'Sequence',
        'label_y': '',
        'data': data
    }
    self.values_data = json.dumps(info)