plot_assignments: Plot cell type assignments in UMAP space.
In gillislab/MetaMarkers: Extract robust markers from multiple datasets

Plot cell type assignments in UMAP space.

plot_assignments(
  assignments,
  umap_coordinates,
  enrichment_threshold = 1,
  point_size = 1,
  rasterize_umap = FALSE
)

`assignments`	A cell type assignment table as returned by assign_cells.
`umap_coordinates`	A (cell x 2) data.frame containing UMAP coordinates, where the ordering of cells is the same as in the score matrix
`enrichment_threshold`	Numeric value defining a threshold below which a cell should be considered unassigned (QC metric). 1 by default.
`point_size`	Numeric value indicating the dot size.
`rasterize_umap`	Boolean. If TRUE, the UMAP part of the figure is rasterized. This is particularly useful for large datasets.