code: def normalize_data(x):
      """
      normalize data to have 0 mean and unit variance
  
      :meta private:
      """
      mn = np.mean(x, axis=0, keepdims=True)
      sd = np.std(x, axis=0, keepdims=True)
      return (x - mn) / (sd + 1e-7)
  
imports: import logging
  import math
  import numpy
  import pandas
  from merlion.models.anomaly.base import DetectorConfig, DetectorBase
  from merlion.post_process.threshold import AdaptiveAggregateAlarms
  from merlion.transform.moving_average import DifferenceTransform
  from merlion.utils import UnivariateTimeSeries, TimeSeries, to_timestamp
label_desc: Use image node_id 3 for calling a global function with example usage: normalize_data(x) and returns: unknown