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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 from_config(cls, config_file=None, profile=None, client=None, endpoint=None, token=None, solver=None, proxy=None, legacy_config_fallback=False, **kwargs):
 """Client factory method to instantiate a client instance from configuration. Configuration values can be specified in multiple ways, ranked in the following order (with 1 the highest ranked):
 1. Values specified as keyword arguments in :func:`from_config()` 2. Values specified as environment variables 3. Values specified in the configuration file Configuration-file format is described in :mod:`dwave.cloud.config`. If the location of the configuration file is not specified, auto-detection searches for existing configuration files in the standard directories of :func:`get_configfile_paths`. If a configuration file explicitly specified, via an argument or environment variable, does not exist or is unreadable, loading fails with :exc:`~dwave.cloud.exceptions.ConfigFileReadError`. Loading fails with :exc:`~dwave.cloud.exceptions.ConfigFileParseError` if the file is readable but invalid as a configuration file. Similarly, if a profile explicitly specified, via an argument or environment variable, is not present in the loaded configuration, loading fails with :exc:`ValueError`. Explicit profile selection also fails if the configuration file is not explicitly specified, detected on the system, or defined via an environment variable. Environment variables: ``DWAVE_CONFIG_FILE``, ``DWAVE_PROFILE``, ``DWAVE_API_CLIENT``, ``DWAVE_API_ENDPOINT``, ``DWAVE_API_TOKEN``, ``DWAVE_API_SOLVER``, ``DWAVE_API_PROXY``. Environment variables are described in :mod:`dwave.cloud.config`. Args: config_file (str/[str]/None/False/True, default=None):
 Path to configuration file. If ``None``, the value is taken from ``DWAVE_CONFIG_FILE`` environment variable if defined. If the environment variable is undefined or empty, auto-detection searches for existing configuration files in the standard directories of :func:`get_configfile_paths`. If ``False``, loading from file is skipped; if ``True``, forces auto-detection (regardless of the ``DWAVE_CONFIG_FILE`` environment variable). profile (str, default=None):
 Profile name (name of the profile section in the configuration file). If undefined, inferred from ``DWAVE_PROFILE`` environment variable if defined. If the environment variable is undefined or empty, a profile is selected in the following order: 1. From the default section if it includes a profile key. 2. The first section (after the default section). 3. If no other section is defined besides ``[defaults]``, the defaults section is promoted and selected. client (str, default=None):
 Client type used for accessing the API. Supported values are ``qpu`` for :class:`dwave.cloud.qpu.Client` and ``sw`` for :class:`dwave.cloud.sw.Client`. endpoint (str, default=None):
 API endpoint URL. token (str, default=None):
 API authorization token. solver (dict/str, default=None):
 Default :term:`solver` features to use in :meth:`~dwave.cloud.client.Client.get_solver`. Defined via dictionary of solver feature constraints (see :meth:`~dwave.cloud.client.Client.get_solvers`). For backward compatibility, a solver name, as a string, is also accepted and converted to ``{"name": <solver name>}``. If undefined, :meth:`~dwave.cloud.client.Client.get_solver` uses a solver definition from environment variables, a configuration file, or falls back to the first available online solver. proxy (str, default=None):
 URL for proxy to use in connections to D-Wave API. Can include username/password, port, scheme, etc. If undefined, client uses the system-level proxy, if defined, or connects directly to the API. legacy_config_fallback (bool, default=False):
 If True and loading from a standard D-Wave Cloud Client configuration file (``dwave.conf``) fails, tries loading a legacy configuration file (``~/.dwrc``). Other Parameters: Unrecognized keys (str):
 All unrecognized keys are passed through to the appropriate client class constructor as string keyword arguments. An explicit key value overrides an identical user-defined key value loaded from a configuration file. Returns: :class:`~dwave.cloud.client.Client` (:class:`dwave.cloud.qpu.Client` or :class:`dwave.cloud.sw.Client`, default=:class:`dwave.cloud.qpu.Client`):
 Appropriate instance of a QPU or software client. Raises: :exc:`~dwave.cloud.exceptions.ConfigFileReadError`: Config file specified or detected could not be opened or read. :exc:`~dwave.cloud.exceptions.ConfigFileParseError`: Config file parse failed. Examples: A variety of examples are given in :mod:`dwave.cloud.config`. This example initializes :class:`~dwave.cloud.client.Client` from an explicitly specified configuration file, "~/jane/my_path_to_config/my_cloud_conf.conf":: """


        # try loading configuration from a preferred new config subsystem
        # (`./dwave.conf`, `~/.config/dwave/dwave.conf`, etc)
        config = load_config(
            config_file=config_file, profile=profile, client=client,
            endpoint=endpoint, token=token, solver=solver, proxy=proxy)
        _LOGGER.debug("Config loaded: %r", config)

        # fallback to legacy `.dwrc` if key variables missing
        if legacy_config_fallback:
            warnings.warn("'legacy_config_fallback' is deprecated, please convert "
                          "your legacy .dwrc file to the new config format.", DeprecationWarning)

            if not config.get('token'):
                config = legacy_load_config(
                    profile=profile, client=client,
                    endpoint=endpoint, token=token, solver=solver, proxy=proxy)
                _LOGGER.debug("Legacy config loaded: %r", config)

        # manual override of other (client-custom) arguments
        config.update(kwargs)

        from dwave.cloud import qpu, sw
        _clients = {'qpu': qpu.Client, 'sw': sw.Client, 'base': cls}
        _client = config.pop('client', None) or 'base'

        _LOGGER.debug("Final config used for %s.Client(): %r", _client, config)
        return _clients[_client](**config)