[BUG] Invalid color cycle save

[mamar828]

Describe the bug
When one color of the color cycle is modified, the saved style file gets corrupted due to an incorrect formatting of the axes.prop_cycle field. Using the style then raises the error :
yaml.constructor.ConstructorError: could not determine a constructor for the tag 'tag:yaml.org,2002:python/object:cycler.Cycler'
in "/.../test_change.yml", line 188, column 20

Lines 188-201 of the file in question :

axes.prop_cycle: !!python/object:cycler.Cycler
    _keys: !!set
      color: null
    _left:
    - color: '#ad8831'
    - color: '#edb73b'
    - color: '#b9503b'
    - color: '#c22811'
    - color: '#695178'
    - color: '#afe6e3'
    - color: '#34a893'
    - color: '#616161'
    _op: null
    _right: null

To Reproduce

• Create a new style
• Modify a color of the color cycle
• Save the style
• Try to open with GraphingLib

Expected behavior
The colors of the color cycle should be saved as a list such as axes.prop_cycle: cycler('color', ['#3e82a0', '#edb73b', '#b9503b', '#8aba4e', '#695178', '#ed893b', '#34a893', '#616161']), but it seems that this is not done properly.

Potential solutions
Revisit the data's exportation to ensure the color cycle is correctly saved.