Arguments
data_frame
object of class data frame containing columns depth,
sample, bp
col
vector of colors for the coverage bars
plot_title
character string for title of plot
x_lab_size
integer specifying the size of the X label
y_lab_size
integer specifying the size of the Y label
facet_lab_size
integer specifying the size of the faceted labels
layers
Additional layers to be plotted, can be a theme but must be a
ggplot layer