remove umap.plot import in _umap.py

[galicae]

I tried installing pyliger on a fresh conda env with different versions of Python and consistently failed to load the library. Steps to reproduce the problem:

> mamba create -n test python=3.10
> mamba activate test
> pip install pyliger
> python
>>> import pyliger

I got the following error:

/Users/myusername/mambaforge/envs/test/lib/python3.10/site-packages/umap/plot.py:20: UserWarning: The umap.plot package requires extra plotting libraries to be installed.
    You can install these via pip using

    pip install umap-learn[plot]

    or via conda using

     conda install pandas matplotlib datashader bokeh holoviews colorcet scikit-image

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/myusername/mambaforge/envs/test/lib/python3.10/site-packages/pyliger/__init__.py", line 5, in <module>
    from .plotting import plot_by_dataset_and_cluster, plot_gene, plot_gene_loadings, plot_spatial
  File "/Users/myusername/mambaforge/envs/test/lib/python3.10/site-packages/pyliger/plotting/__init__.py", line 3, in <module>
    from ._gene_loadings import plot_gene_loadings
  File "/Users/myusername/mambaforge/envs/test/lib/python3.10/site-packages/pyliger/plotting/_gene_loadings.py", line 7, in <module>
    from ..tools import calc_dataset_specificity, get_factor_markers
  File "/Users/myusername/mambaforge/envs/test/lib/python3.10/site-packages/pyliger/tools/__init__.py", line 2, in <module>
    from ._umap import run_umap
  File "/Users/myusername/mambaforge/envs/test/lib/python3.10/site-packages/pyliger/tools/_umap.py", line 2, in <module>
    import umap.plot
  File "/Users/myusername/mambaforge/envs/test/lib/python3.10/site-packages/umap/plot.py", line 31, in <module>
    raise ImportError(
ImportError: umap.plot requires pandas matplotlib datashader bokeh holoviews scikit-image and colorcet to be installed

By going to the mamba installation directory and removing the offending line I was able to circumvent the issue. Maybe a forgotten import statement that could be removed?

pyliger/src/pyliger/tools/_umap.py

Line 2 in 2ae9add

import umap.plot