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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 scrape_file(self, file, encoding=None, base_url=None):
        '''Scrape a file for links.

        See :meth:`scrape` for the return value.
        '''
        elements = self.iter_elements(file, encoding=encoding)

        link_contexts = set()

        link_infos = self._element_walker.iter_links(elements)

        for link_info in link_infos:
            element_base_url = base_url

            if link_info.base_link:
                clean_base_url = clean_link_soup(link_info.base_link)

                if element_base_url and base_url:
                    element_base_url = urljoin_safe(
                        base_url, clean_base_url
                    ) or base_url

            if element_base_url:
                url = urljoin_safe(
                    element_base_url,
                    clean_link_soup(link_info.link),
                    allow_fragments=False
                )
            else:
                url = clean_link_soup(link_info.link)

            if url:
                link_contexts.add(LinkContext(
                    url,
                    inline=link_info.inline,
                    linked=link_info.linked,
                    link_type=link_info.link_type,
                    extra=link_info
                ))

        scrape_result = ScrapeResult(link_contexts, encoding)
        scrape_result['base_url'] = base_url
        return scrape_result