Validate some key assumptions about the fish object's data
validateInputs(frac.table, parents, nest.level, clone.labels)
A numeric matrix containing tumor fraction estimates for all clones at all timepoints
An integer vector specifying parental relationships between clones
An integer vector specifying how deeply a given clone is nested in the overall hierarchy
An integer vector specifying how deeply a given clone is nested in the overall hierarchy
No return value - stops execution with an error if invalid inputs are detected