def __init__(self, url, comes_from=None, requires_python=None):<EOL>
<EOL>if url.startswith('<STR_LIT>'):<EOL><INDENT>url = path_to_url(url)<EOL><DEDENT>self.url = url<EOL>self.comes_from = comes_from<EOL>self.requires_python = requires_python if requires_python else None<EOL>super(Link, self).__init__(<EOL>key=(self.url),<EOL>defining_class=Link<EOL>)<EOL>
url:
    url of the resource pointed to (href of the link)
comes_from:
    instance of HTMLPage where the link was found, or string.
requires_python:
    String containing the `Requires-Python` metadata field, specified
    in PEP 345. This may be specified by a data-requires-python
    attribute in the HTML link tag, as described in PEP 503.