How to use the coverage.files.canonical_filename function in coverage

def assertMatches(self, matcher, filepath, matches):
        """The `matcher` should agree with `matches` about `filepath`."""
        canonical = files.canonical_filename(filepath)
        self.assertEqual(
            matcher.match(canonical), matches,
            "File %s should have matched as %s" % (filepath, matches)
        )

def assert_mapped(self, aliases, inp, out):
        """Assert that `inp` mapped through `aliases` produces `out`.

        `out` is canonicalized first, since aliases always produce
        canonicalized paths.

        """
        aliases.pprint()
        print(inp)
        print(out)
        self.assertEqual(aliases.map(inp), files.canonical_filename(out))

def canonical_path(morf, directory=False):
    """Return the canonical path of the module or file `morf`.

    If the module is a package, then return its directory. If it is a
    module, then return its file, unless `directory` is True, in which
    case return its enclosing directory.

    """
    morf_path = canonical_filename(source_for_morf(morf))
    if morf_path.endswith("__init__.py") or directory:
        morf_path = os.path.split(morf_path)[0]
    return morf_path

# Try the plugins, see if they have an opinion about the file.
        plugin = None
        for plugin in self.plugins.file_tracers:
            if not plugin._coverage_enabled:
                continue

            try:
                file_tracer = plugin.file_tracer(canonical)
                if file_tracer is not None:
                    file_tracer._coverage_plugin = plugin
                    disp.trace = True
                    disp.file_tracer = file_tracer
                    if file_tracer.has_dynamic_source_filename():
                        disp.has_dynamic_filename = True
                    else:
                        disp.source_filename = canonical_filename(
                            file_tracer.source_filename()
                        )
                    break
            except Exception:
                self.warn(
                    "Disabling plug-in %r due to an exception:" % (plugin._coverage_plugin_name)
                )
                traceback.print_exc()
                plugin._coverage_enabled = False
                continue
        else:
            # No plugin wanted it: it's Python.
            disp.trace = True
            disp.source_filename = canonical

        if not disp.has_dynamic_filename:

def __init__(self, morf, coverage=None):
        self.coverage = coverage

        filename = source_for_morf(morf)

        super(PythonFileReporter, self).__init__(files.canonical_filename(filename))

        if hasattr(morf, '__name__'):
            name = morf.__name__.replace(".", os.sep)
            if os.path.basename(filename).startswith('__init__.'):
                name += os.sep + "__init__"
            name += ".py"
            name = files.unicode_filename(name)
        else:
            name = files.relative_filename(filename)
        self.relname = name

        self._source = None
        self._parser = None
        self._excluded = None

def _find_dep_file_path(main_file, file_path, relative_path_search=False):
    abs_path = os.path.abspath(file_path)
    if not os.path.exists(abs_path) and (file_path.endswith('.pxi') or
                                         relative_path_search):
        # files are looked up relative to the main source file
        rel_file_path = os.path.join(os.path.dirname(main_file), file_path)
        if os.path.exists(rel_file_path):
            abs_path = os.path.abspath(rel_file_path)
    # search sys.path for external locations if a valid file hasn't been found
    if not os.path.exists(abs_path):
        for sys_path in sys.path:
            test_path = os.path.realpath(os.path.join(sys_path, file_path))
            if os.path.exists(test_path):
                return canonical_filename(test_path)
    return canonical_filename(abs_path)

def _find_dep_file_path(main_file, file_path):
        # file_path is already arcadia root relative
        return canonical_filename(file_path)

def _find_dep_file_path(main_file, file_path, relative_path_search=False):
    abs_path = os.path.abspath(file_path)
    if not os.path.exists(abs_path) and (file_path.endswith('.pxi') or
                                         relative_path_search):
        # files are looked up relative to the main source file
        rel_file_path = os.path.join(os.path.dirname(main_file), file_path)
        if os.path.exists(rel_file_path):
            abs_path = os.path.abspath(rel_file_path)
    # search sys.path for external locations if a valid file hasn't been found
    if not os.path.exists(abs_path):
        for sys_path in sys.path:
            test_path = os.path.realpath(os.path.join(sys_path, file_path))
            if os.path.exists(test_path):
                return canonical_filename(test_path)
    return canonical_filename(abs_path)