I have defined two enums with attributes. When I want to access an enum element by specifying its attribute it works for enum `A` (one attribute) but not for enum `B` (two attributes):

```
from enum import Enum

class A(Enum):
    ValOne = ('One')
    ValTwo = ('Two')

    def __init__(self, num):
        self.num = num

class B(Enum):
    ValOne = ('Val', 'One')
    ValTwo = ('Val', 'Two')

    def __init__(self, val, num):
        self.val = val
        self.num = num

print(A('One'))
print(B('Val', 'One'))

```

I get the following output:

```
A.ValOne
Traceback (most recent call last):
  File "test.py", line 19, in <module>
    print(B('Val', 'One'))
  File "/usr/lib/python3.8/enum.py", line 341, in __call__
    return cls._create_(
  File "/usr/lib/python3.8/enum.py", line 444, in _create_
    _, first_enum = cls._get_mixins_(cls, bases)
  File "/usr/lib/python3.8/enum.py", line 576, in _get_mixins_
    raise TypeError("Cannot extend enumerations")
TypeError: Cannot extend enumerations

```

What am I missing here?