Function to visualize the growth coefficients for each clone and lineage.
Arguments
- x
- a mvnmm object. 
- highlight
- a vector of clusters IDs to highlight in the plot. 
- min_frac
- min_frac numeric value in - [0,1]representing the minimum abundance to highlight a clone.
- mutations
- Boolean. If set to - TRUE, the growth will be visualize for each cluster of mutations.
- timepoints_to_int
- a list to map each - timepointvalue to an integer.
- fit
- add 
