code: def quantity(*args):
      
      if len(args) == 1:
          if isinstance(args[0], str):
              # use copy constructor to create quantity from string
              return Quantity(from_string(args[0]))
          elif isinstance(args[0], dict):
              if hasattr(args[0]["value"], "__len__"):
                  return QuantVec(from_dict_v(args[0]))
              else:
                  return Quantity(from_dict(args[0]))
          elif isinstance(args[0], Quantity) or isinstance(args[0], QuantVec):
              return args[0]
          else:
              raise TypeError("Invalid argument type for")
      else:
          if hasattr(args[0], "__len__"):
              return QuantVec(*args)
          else:
              return Quantity(*args)
docs: Create a quantity. This can be from a scalar or vector.
  
      Example::
  
        q1 = quantity(1.0, "km/s")
        q2 = quantity("1km/s")
        q1 = quantity([1.0,2.0], "km/s")