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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 get_config_paths(config_name):
 # pragma: no test """ Return a list of config files paths to try in order, given config file name and possibly a user-specified path. For Windows platforms, there are several paths that can be tried to retrieve the netrc file. There is, however, no "standard way" of doing things. A brief recap of the situation (all file paths are written in Unix convention):
 1. By default, Windows does not define a $HOME path. However, some people might define one manually, and many command-line tools imported from Unix will search the $HOME environment variable first. This 2. Windows defines two 'user paths': $USERPROFILE, and the concatenation of the two variables $HOMEDRIVE and $HOMEPATH. Both of these paths point by default to the same location, e.g. C:\\Users\\Username 3. $USERPROFILE cannot be changed, however $HOMEDRIVE and $HOMEPATH can be changed. They are originally intended to be the equivalent of the $HOME path, but there are many known issues with them 4. As for the name of the file itself, most of the tools ported from Unix will use the standard '.dotfile' scheme, but some of these will instead use "_dotfile". Of the latter, the two notable exceptions are vim, which will first try '_vimrc' before '.vimrc' (but it will try both) and git, which will require the user to name its netrc file '_netrc'. Relevant links : http://markmail.org/message/i33ldu4xl5aterrr http://markmail.org/message/wbzs4gmtvkbewgxi http://stackoverflow.com/questions/6031214/ Because the whole thing is a mess, I suggest we tried various sensible defaults until we succeed or have depleted all possibilities. """


    if platform.system() != 'Windows':
        return [None]

    # Now, we only treat the case of Windows
    env_vars = [["HOME"],
                ["HOMEDRIVE", "HOMEPATH"],
                ["USERPROFILE"],
                ["SYSTEMDRIVE"]]

    env_dirs = []
    for var_list in env_vars:

        var_values = [_getenv_or_empty(var) for var in var_list]

        directory = ''.join(var_values)
        if not directory:
            logging.debug('Environment var(s) %s not defined, skipping',
                          var_list)
        else:
            env_dirs.append(directory)

    additional_dirs = ["C:", ""]

    all_dirs = env_dirs + additional_dirs

    leading_chars = [".", "_"]

    res = [''.join([directory, os.sep, lc, config_name])
           for directory in all_dirs
           for lc in leading_chars]

    return res