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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 read_configuration(key, path=None, default=None, single_config=False, fallback_to_env=True):
 """ Read configuration from a file, Docker config or secret or from the environment variables. :param key: the configuration key :param path: the path of the configuration file (regular file or Docker config or secret) :param default: the default value when not found elsewhere (default: `None`) :param single_config: treat the configuration file as containing the full configuration, otherwise the file is expected to be a '=' separated key-value list line by line (default: `False`) :param fallback_to_env: look for the configuration key in the environment variables if not found elsewhere (default: `True`) """


    if path and os.path.exists(path):
        with open(path, 'r') as config_file:
            if single_config:
                return config_file.read()

            for line in config_file:
                if line.startswith('%s=' % key):
                    return line.split('=', 1)[1].strip()

    if fallback_to_env and key in os.environ:
        return os.environ[key]

    return default