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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def binder_spec_from_github_url(github_url):
 """ Converts GitHub origin into a Binder spec. For example: git@github.com:SamLau95/nbinteract.git -> SamLau95/nbinteract/master https://github.com/Calebs97/riemann_book -> Calebs97/riemann_book/master """

    tokens = re.split(r'/|:', github_url.replace('.git', ''))
    # The username and reponame are the last two tokens
    return '{}/{}/master'.format(tokens[-2], tokens[-1])