在哪里可以找到python中str方法的实现？

Question

有一天，我只是想知道如何在python中实现str，list和map方法。

当我尝试对split（）进行“定义”时，代码看起来像

def split(self, sep=None, maxsplit=-1): # real signature unknown; restored from __doc__
    """
    S.split(sep=None, maxsplit=-1) -> list of strings

    Return a list of the words in S, using sep as the
    delimiter string.  If maxsplit is given, at most maxsplit
    splits are done. If sep is not specified or is None, any
    whitespace string is a separator and empty strings are
    removed from the result.
    """
    return []

如何找到这些方法的代码？