<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _get_available_extensions():
 """Get a list of available file extensions to make it easy for tab-completion and exception handling. """

    extensions = []

    # from filenames
    parsers_dir = os.path.join(os.path.dirname(__file__))
    glob_filename = os.path.join(parsers_dir, "*" + _FILENAME_SUFFIX + ".py")
    ext_re = re.compile(glob_filename.replace('*', "(?P<ext>\w+)"))
    for filename in glob.glob(glob_filename):
        ext_match = ext_re.match(filename)
        ext = ext_match.groups()[0]
        extensions.append(ext)
        extensions.append('.' + ext)

    # from relevant synonyms (don't use the '' synonym)
    for ext in EXTENSION_SYNONYMS.keys():
        if ext:
            extensions.append(ext)
            extensions.append(ext.replace('.', '', 1))
    extensions.sort()
    return extensions