new_contents: from bigbang.archive import Archive
  import bigbang.parse as parse
  import bigbang.graph as graph
  import bigbang.mailman as mailman
  import bigbang.process as process
  import matplotlib.pyplot as plt
  import networkx as nx
  import numpy as np
  import pandas as pd
  from pprint import pprint as pp
  import pytz
  
  def duration(exchanges, A, B):
      AtoB = exchanges[exchanges['From_original']==A]
      AtoB = AtoB[AtoB['From_response']==B]
      BtoA = exchanges[exchanges['From_original']==B]
      BtoA = BtoA[BtoA['From_response']==A]
      return max(max(AtoB['Date']), max(BtoA['Date'])) - min(min(AtoB['Date']), min(BtoA['Date']))
      
  def num_replies(exchanges, A, B):
      AtoB = exchanges[exchanges['From_original']==A]
      AtoB = AtoB[AtoB['From_response']==B]
      BtoA = exchanges[exchanges['From_original']==B]
      BtoA = BtoA[BtoA['From_response']==A]
      return (len(AtoB), len(BtoA))
      
  def reciprocity(exchanges, A, B):
      num = num_replies(exchanges, A, B)
      return float(min(num))/max(num)
  
subject: Create twopeople.py