code: def transform(x):
          
          try:
              x = date2num(x)
          except AttributeError:
              # numpy datetime64
              # This is not ideal because the operations do not
              # preserve the np.datetime64 type. May be need
              # a datetime64_trans
              x = [pd.Timestamp(item) for item in x]
              x = date2num(x)
          return x
docs: Transform from date to a numerical format