docs: def _build_session(username, password, trans_label=None):
      '''
      Create a session to be used when connecting to iControl REST.
      '''
  
      bigip = requests.session()
      bigip.auth = (username, password)
      bigip.verify = False
      bigip.headers.update({'Content-Type': 'application/json'})
  
      if trans_label:
          #pull the trans id from the grain
          trans_id = __salt__['grains.get']('bigip_f5_trans:{label}'.format(label=trans_label))
  
          if trans_id:
              bigip.headers.update({'X-F5-REST-Coordination-Id': trans_id})
          else:
              bigip.headers.update({'X-F5-REST-Coordination-Id': None})
  
      return bigip