code: def _get_chart_info(df, vtype, cat, prep, callers):
      
      maxval_raw = max(list(df["value.floor"]))
      curdf = df[(df["variant.type"] == vtype) & (df["category"] == cat)
                 & (df["bamprep"] == prep)]
      vals = []
      labels = []
      for c in callers:
          row = curdf[df["caller"] == c]
          if len(row) > 0:
              vals.append(list(row["value.floor"])[0])
              labels.append(list(row["value"])[0])
          else:
              vals.append(1)
              labels.append("")
      return vals, labels, maxval_raw
docs: Retrieve values for a specific variant type, category and prep method.