Providing a label name in plotly express

Hi I am wondering how to give a label name when using plotly express where the data is not in the form of a DataFrame. Its not possible to use the keyword argument name when using px.line. However it is a possible when using px.scatter function.

As a result in the example below I end up with a legend name only for the second trace.

I am aware this can be easily done using plotly.graph_objs but wondering how to do in plotly.express

import plotly.express as px 
history_dict = history.history

p1 = px.line(
    x = np.arange(0,20),
    y = history_dict["loss"],
    # error if name keyword argument used here.
    title = "Training and Validation Loss",   
)

p1.add_scatter(
    x = np.arange(0,20),
    y = history_dict["val_loss"],
    mode = "lines",
    name = "val loss"
)

p1.update_layout(xaxis_title = "epochs", yaxis_title = "loss")