text: import pandas as pd
  
  
  def df_prep(x, y=None, labels=None):
      if y is not None:
          df = pd.DataFrame(y, columns=labels)
          df["x"] = x
      else:
          df = pd.DataFrame(x, columns=labels)
          df["x"] = df.index
      df = df.melt(id_vars="x", value_name="y", var_name="series")
      return df
  