old_contents: """
  This package defines an adapter layer for writing wrappers of existing
  HTTP clients (Requests, aiohttp, etc.) so they can handle requests built by
  Uplink's high-level, declarative API.
  
  We refer to this layer as the backend, as these adapters handle the
  actual HTTP client logic (i.e., making a request to a server).
  
  Todo:
      At some point, we may want to expose this layer to the user, so
      they can create custom adapters.
  """
  # Local imports
  from uplink import utils
  from uplink.clients import interfaces, register
  from uplink.clients.register import DEFAULT_CLIENT, get_client
  from uplink.clients.requests_ import RequestsClient
  from uplink.clients.twisted_ import TwistedClient
  
  
  @register.handler
  def _client_class_handler(key):
      if utils.is_subclass(key, interfaces.HttpClientAdapter):
          return key()
  
  
  try:
      from uplink.clients.aiohttp_ import AiohttpClient
  except (ImportError, SyntaxError) as error:  # pragma: no cover
  
      class AiohttpClient(interfaces.HttpClientAdapter):
          def __init__(self, *args, **kwargs):
              raise NotImplementedError(
                  "Failed to load `aiohttp` client: you may be using a version "
                  "of Python below 3.3. `aiohttp` requires Python 3.4+."
              )
  
          def create_request(self):
              pass
  
  
  __all__ = [
      "RequestsClient",
      "AiohttpClient",
      "TwistedClient",
      "DEFAULT_CLIENT",
      "get_client",
  ]
  
  register.set_default_client(RequestsClient)
  
new_contents: """
  This package defines an adapter layer for writing wrappers of existing
  HTTP clients (Requests, aiohttp, etc.) so they can handle requests built by
  Uplink's high-level, declarative API.
  
  We refer to this layer as the backend, as these adapters handle the
  actual HTTP client logic (i.e., making a request to a server).
  
  Todo:
      At some point, we may want to expose this layer to the user, so
      they can create custom adapters.
  """
  # Local imports
  from uplink import utils
  from uplink.clients import interfaces, register
  from uplink.clients.register import DEFAULT_CLIENT, get_client
  from uplink.clients.requests_ import RequestsClient
  from uplink.clients.twisted_ import TwistedClient
  
  
  @register.handler
  def _client_class_handler(key):
      if utils.is_subclass(key, interfaces.HttpClientAdapter):
          return key()
  
  
  try:
      from uplink.clients.aiohttp_ import AiohttpClient
  except (ImportError, SyntaxError):  # pragma: no cover
  
      class AiohttpClient(interfaces.HttpClientAdapter):
          def __init__(self, *args, **kwargs):
              raise NotImplementedError(
                  "Failed to load `aiohttp` client: you may be using a version "
                  "of Python below 3.3. `aiohttp` requires Python 3.4+."
              )
  
          def create_request(self):
              pass
  
  
  __all__ = [
      "RequestsClient",
      "AiohttpClient",
      "TwistedClient",
      "DEFAULT_CLIENT",
      "get_client",
  ]
  
  register.set_default_client(RequestsClient)
  
subject: Remove unused local variable