The debugger calls f_locals on all frames

[impact27]

To reproduce, debug the following code line by line, pressing next on each line:

import pandas as pd
import plotly.express as px
import plotly.io as pio
pio.renderers.default='svg'  # this line required for plots to show in Spyder Plots panel

df = pd.DataFrame([
    dict(Task="Job A", Start='2009-01-01', Finish='2009-02-28'),
    dict(Task="Job B", Start='2009-03-05', Finish='2009-04-15'),
    dict(Task="Job C", Start='2009-02-20', Finish='2009-05-30')
])

fig = px.timeline(df, x_start="Start", x_end="Finish", y="Task")
fig.update_yaxes(autorange="reversed") # otherwise tasks are listed from the bottom up
fig.show()

This results in: AttributeError: 'NoneType' object has no attribute 'layout'

The problem is that the IPython debugger calls frame.f_locals on every step on every call. Calling frame.f_locals will reset the locals of the frame, and plotly does this:
https://github.com/plotly/plotly.py/blob/a4b9887bc7d5f5151b803221fa650291840d150e/packages/python/plotly/plotly/express/_chart_types.py#L424

The second issue is that looping on all frames on each python instruction is slow:
spyder-ide/spyder#20571

[ccordoba12]

@mlucool, our solution was to disable the IPython debuggerskip functionality (see spyder-ide/spyder-kernels#458). That's not that useful by itself because users need to mark what frames they want to skip first.

[mlucool]

Thanks @ccordoba12. I deleted my comment in part because it turns out debuggerskip was not adding that much for that specific test (that is, it matters, but not as much as something I am yet to figure out)