message: reformated the python test
diff: import pandas as pd
  import numpy as np
  -from datetime import datetime, timedelta
  -days = pd.date_range("1970-01-01", "2019-08-15", freq='1S')
  +days = pd.date_range("1970-01-01", "2019-08-15", freq='S')
  normal = np.random.normal(size=len(days))
  log_normal = np.random.lognormal(size=len(days))
  exponential = np.random.exponential(size=len(days))
  -df = pd.DataFrame({"date": days, "normal": normal, "log_normal": log_normal, "exponential": exponential})
  +
  +df = pd.DataFrame({"date": days,
  + "normal": normal,
  + "log_normal": log_normal,
  + "exponential": exponential,
  + })
  df.set_index("date")
  +
  df["normal"].mean()
  df["log_normal"].mean()
  df["exponential"].mean()
  