The constructor should not use **kwargs to improve usability of the API

[devfoo-one]

Better, define a speaking constructor and add a class method from_arguments()

https://www.erol.si/2016/01/python-and-multiple-constructors/

[devfoo-one]

e.g.

class Span(object):
    def __init__(self, uid: int = None, begin: int = 0, length: int = None, text: str = ''):
        self.uid = uid
        self.begin = begin
        self.text = text
        if length is None:
            length = len(text)
        self.length = length

    @classmethod
    def from_arguments(cls, **kwargs):
        return cls(
            uid=kwargs.get('uid', None),
            begin=kwargs.get('begin', 0),
            length=kwargs.get('length', 0),
            text=kwargs.get('text', "")
        )