ImportError with Plotly 7.0.0: create_distplot was removed from plotly.figure_factory #384

Describe the bug
openseries 2.1.9 cannot be imported when Plotly 7.0.0 is installed. _common_model.py imports create_distplot from plotly.figure_factory at module load time, but that function was removed in Plotly 7.

The declared dependency is plotly>=5.18.0 with no upper bound, so a fresh install (or lockfile update) now resolves Plotly 7.0.0 and the package fails before any openseries API is used.

To Reproduce

1. Install openseries==2.1.9 with plotly==7.0.0 (for example via pip install openseries plotly after Plotly 7.0.0 was released).
2. Run:

from openseries import OpenTimeSeries

Expected behavior
openseries imports successfully, and plot_histogram(..., plot_type="lines") still works.

Actual behavior

ImportError: cannot import name 'create_distplot' from 'plotly.figure_factory'

Traceback:

File ".../openseries/__init__.py", line 13, in <module>
    from .frame import OpenFrame
File ".../openseries/frame.py", line 52, in <module>
    from ._common_model import _calculate_time_factor, _CommonModel, _get_base_column_data
File ".../openseries/_common_model.py", line 61, in <module>
    from plotly.figure_factory import create_distplot
ImportError: cannot import name 'create_distplot' from 'plotly.figure_factory'

Environment

• openseries 2.1.9
• plotly 7.0.0
• Python 3.14 (also expected on 3.11–3.13)
• macOS

Additional Information
Plotly 7.0.0 (released 2026-08-25) removed several deprecated Figure Factory helpers, including create_distplot:
https://github.com/plotly/plotly.py/releases/tag/v7.0.0

The import is here:

https://github.com/CaptorAB/openseries/blob/master/openseries/_common_model.py#L61

It is used in plot_histogram when plot_type == "lines":

https://github.com/CaptorAB/openseries/blob/master/openseries/_common_model.py#L1440

Suggested fixes:

1. Cap the dependency immediately: plotly>=5.18.0,<7.
2. Replace create_distplot with a Plotly Express / graph-objects equivalent (Plotly recommends plotly.express.histogram with marginal="rug").
3. Optionally lazy-import the plotting helper so a Plotly 7 install does not break from openseries import OpenTimeSeries even before plot_histogram is called.

Until this is released, downstream projects can work around it with plotly>=5.18.0,<7.