code: def calc_bias_and_variance(x, true_mean):
      sample_mean = np.mean(x)
      bias = np.mean(np.abs(sample_mean - true_mean))
      variance = np.mean((x - sample_mean) ** 2)
      return (bias, variance)
  
file_path: trax/trax/rl/advantages_test.py
imports: import functools
  from absl.testing import absltest
  from absl.testing import parameterized
  import numpy
  from trax.rl import advantages
label_desc: Use image node_id 1 for calling a global function with example usage: calc_bias_and_variance(x, true_mean) and returns: bias,  variance