parameters: (self, fd, callback)
docstring: Start watching the file descriptor for read availability and then call
          the callback.
docstring_summary: Start watching the file descriptor for read availability and then call
          the callback.
docstring_tokens: Start watching the file descriptor for read availability and then call the callback .
function: def add_reader(self, fd, callback):
          """
          Start watching the file descriptor for read availability and then call
          the callback.
          """
function_tokens: def add_reader ( self , fd , callback ) :