Can't login without email even though it's supposed to be optional

[Mutusen]

Hi, the documentation says "Optional either username or email can be used, or both. It returns response with token along with it for authentication" but it doesn't work if I don't provide an email address.

In api/serializers.py:

class UserLoginSerializer(serializers.Serializer):
    email = serializers.EmailField(required=False)
    username = serializers.CharField(required=False)
    password = serializers.CharField()
    def validate(self, data):
        email = data['email']
        if not 'email' in data and not 'username' in data :
            raise serializers.ValidationError('Enter Username Or Email')        
        return data

I suggest deleting the line email = data['email'] because the email variable is not used in this function and causes an error if there is no email given.