input: Write a python function to calculate the p-value from a given Z-score.
  assert round(pvalue(1.96), 5) == 0.04999
  assert round(pvalue(2.58), 5) == 0.00994
  assert round(pvalue(0), 5) == 1.0
output: def pvalue(z):
      from scipy.stats import norm
      return 2 * (1 - norm.cdf(abs(z)))