docs: def shellinit(cli):
          """Implements the waybill shims in the active shell"""
          output = 'eval echo "Initializing Waybills"'
          if which('docker') is None:
              raise ValueError("Unable to find program 'docker'.  Please make sure it is installed and setup properly")
          for waybill in cli.get_waybills():
              output += ' && source {0}'.format(waybill)
          return output