def annotate_file(self, fr: FileReporter, analysis: Analysis) -> None:
        """Annotate a single file.

        `fr` is the FileReporter for the file to annotate.

        """
        statements = sorted(analysis.statements)
        missing = sorted(analysis.missing)
        excluded = sorted(analysis.excluded)

        if self.directory:
            ensure_dir(self.directory)
            dest_file = os.path.join(self.directory, flat_rootname(fr.relative_filename()))
            assert dest_file.endswith("_py")
            dest_file = dest_file[:-3] + ".py"
        else:
            dest_file = fr.filename
        dest_file += ",cover"

        with open(dest_file, "w", encoding="utf-8") as dest:
            i = j = 0
            covered = True
            source = fr.source()
            for lineno, line in enumerate(source.splitlines(True), start=1):
                while i < len(statements) and statements[i] < lineno:
                    i += 1
                while j < len(missing) and missing[j] < lineno:
                    j += 1
                if i < len(statements) and statements[i] == lineno:
                    covered = j >= len(missing) or missing[j] > lineno
                if self.blank_re.match(line):
                    dest.write("  ")
                elif self.else_re.match(line):
                    # Special logic for lines containing only "else:".
                    if j >= len(missing):
                        dest.write("> ")
                    elif statements[i] == missing[j]:
                        dest.write("! ")
                    else:
                        dest.write("> ")
                elif lineno in excluded:
                    dest.write("- ")
                elif covered:
                    dest.write("> ")
                else:
                    dest.write("! ")

                dest.write(line)
Annotate a single file.

        `fr` is the FileReporter for the file to annotate.

        
coverage/annotate.py