content: """
  OAuth2 Authentication implementation for HTTPX.
  
  Implements authorization code flow with PKCE and automatic token refresh.
  """
  
  from mcp.client.auth.exceptions import OAuthFlowError, OAuthRegistrationError, OAuthTokenError
  from mcp.client.auth.oauth2 import (
      OAuthClientProvider,
      PKCEParameters,
      TokenStorage,
  )
  
  __all__ = [
      "OAuthClientProvider",
      "OAuthFlowError",
      "OAuthRegistrationError",
      "OAuthTokenError",
      "PKCEParameters",
      "TokenStorage",
  ]
  