call back to a Go function. The #cgo nocallback directive may be used to
tell the compiler that these preparations are not necessary.
If the nocallback directive is used and the C function does call back into
Go code, the program will panic.

For example:

	// #cgo nocallback cFunctionName

# Special cases

A few special C types which would normally be represented by a pointer

*   `tf.experimental.StructuredTensor`

    *   Introduced `tf.experimental.StructuredTensor`, which provides a flexible
        and Tensorflow-native way to encode structured data such as protocol
        buffers or pandas dataframes.

*   `tf.keras`:

    *   Added method `get_metrics_result()` to `tf.keras.models.Model`.
        *   Returns the current metrics values of the model as a dict.

pkg log, func Fatalf(string, ...interface{})
pkg log, func Fatalln(...interface{})
pkg log, func Flags() int
pkg log, func New(io.Writer, string, int) *Logger
pkg log, func Panic(...interface{})
pkg log, func Panicf(string, ...interface{})
pkg log, func Panicln(...interface{})
pkg log, func Prefix() string
pkg log, func Print(...interface{})
pkg log, func Printf(string, ...interface{})
pkg log, func Println(...interface{})