[BUG] Dash 2.1 - RadioItems doesn't take value as 2nd positional argument

[LiamConnors]

Dash 2.1 - RadioItems doesn't take value as 2nd positional argument.

• replace the result of pip list | grep dash below

dash                 2.1

Describe the bug

Running the following app where value is provided as a keyword argument loads with Montreal selected:

import dash_core_components as dcc
import dash

app = dash.Dash(__name__)

app.layout = dcc.RadioItems(
    options=[
        {'label': 'New York City', 'value': 'NYC'},
        {'label': 'Montréal', 'value': 'MTL'},
        {'label': 'San Francisco', 'value': 'SF'}
    ],
    value='MTL'
)

if __name__ == "__main__":
    app.run_server(debug=True)

Running it with positional arguments for options and value, no value is selected on load:

import dash_core_components as dcc
import dash

app = dash.Dash(__name__)

app.layout = dcc.RadioItems(
    [
        {'label': 'New York City', 'value': 'NYC'},
        {'label': 'Montréal', 'value': 'MTL'},
        {'label': 'San Francisco', 'value': 'SF'}
    ],
    'MTL'
)

if __name__ == "__main__":
    app.run_server(debug=True)

Expected behavior

Montreal should show on load as the value is set to 'MTL' with the second positional argument