code: def length(
              cls, request,
              vector: (Ptypes.body,
                       Vector('The vector to analyse.'))) -> [
              (200, 'Ok', Float),
              (400, 'Wrong vector format')]:
          '''Return the modulo of a vector.'''
          log.info('Computing the length of vector {}'.format(vector))
          try:
              Respond(200, sqrt(vector['x'] ** 2 +
                                vector['y'] ** 2 +
                                vector.get('z', 0) ** 2))
          except ValueError:
              Respond(400f length(
              cls, request,
              vector: (Ptypes.body,
                       Vector('The vector to analyse.'))) -> [
              (200, 'Ok', Float),
              (400, 'Wrong vector format')]:
          '''Return the modulo of a vector.'''
          log.info('Computing the length of vector {}'.format(vector))
          try:
              Respond(200, sqrt(vector['x'] ** 2 +
                                vector['y'] ** 2 +
                                vector.get('z', 0) ** 2))
          except ValueError:
              Respond(400)
docs: Return the modulo of a vector.