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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 _dump_impl():
 # type: () -> List[FunctionData] """Internal implementation for dump_stats and dumps_stats"""

    filtered_signatures = _filter_types(collected_signatures)
    sorted_by_file = sorted(iteritems(filtered_signatures),
                            key=(lambda p: (p[0].path, p[0].line, p[0].func_name)))
    res = []  # type: List[FunctionData]
    for function_key, signatures in sorted_by_file:
        comments = [_make_type_comment(args, ret_type) for args, ret_type in signatures]
        res.append(
            {
                'path': function_key.path,
                'line': function_key.line,
                'func_name': function_key.func_name,
                'type_comments': comments,
                'samples': num_samples.get(function_key, 0),
            }
        )
    return res