   For example, directory to be deleted may be non-empty,
   an rmdir operation is applied to a non-directory, etc.
   """
+  @spec failed_precondition :: t
   def failed_precondition, do: 9
 
   @doc """


  An example of where this error may be returned is
  if a Status value received from another address space belongs to
  an error-space that is not known in this address space.  Also
  errors raised by APIs that do not return enough error information
  may be converted to this error.
  """
  def unknown, do: 2

  @doc """


  E.g., seeking or reading past end of file.
  """
  @spec out_of_range :: t
  def out_of_range, do: 11

  @doc """
  Operation is not implemented or not supported/enabled in this service.
  """
  @spec unimplemented :: t
  def unimplemented, do: 12

  @doc """
