input: Write a function to detect fraud in numerical data.
  assert detect_fraud(np.array([[1, 2], [2, 3], [100, 200]])) == [np.array([100, 200])]
  assert detect_fraud(np.array([[1, 1], [1, 1], [1, 1]])) == []
  assert detect_fraud(np.array([[10, 20], [15, 25], [30, 40]])) == []
output: import numpy as np
  
  def detect_fraud(data):
      threshold = 3
      means = np.mean(data, axis=0)
      std_devs = np.std(data, axis=0)
  
      def is_outlier(row):
          return any(abs(row[i] - means[i]) > threshold * std_devs[i] for i in range(len(row)))
  
      return [row for row in data if is_outlier(row)]