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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 _remote_file_size(url=None, file_name=None, pb_dir=None):
 """ Get the remote file size in bytes Parameters url : str, optional The full url of the file. Use this option to explicitly state the full url. file_name : str, optional The base file name. Use this argument along with pb_dir if you want the full url to be constructed. pb_dir : str, optional The base file name. Use this argument along with file_name if you want the full url to be constructed. Returns ------- remote_file_size : int Size of the file in bytes """


    # Option to construct the url
    if file_name and pb_dir:
        url = posixpath.join(config.db_index_url, pb_dir, file_name)

    response = requests.head(url, headers={'Accept-Encoding': 'identity'})
    # Raise HTTPError if invalid url
    response.raise_for_status()

    # Supposed size of the file
    remote_file_size = int(response.headers['content-length'])

    return remote_file_size