Creates a new #GBytes which references the data mapped from @file.
The mapped contents of the file must not be modified after creating this
bytes object, because a #GBytes should be immutable.
Return: A newly allocated #GBytes referencing data
from @file
Creates a new #GBytes which references the data mapped from @file. The mapped contents of the file must not be modified after creating this bytes object, because a #GBytes should be immutable.
Return: A newly allocated #GBytes referencing data from @file