'Return a read-write buffer object that references the raw C data
pointed to by the given \'cdata\'.  The \'cdata\' must be a pointer or
an array.  Can be passed to functions expecting a buffer, or directly
manipulated with:
buf[:]          get a copy of it in a regular string, or
buf[idx]        as a single character
buf[:] = ...
buf[idx] = ...  change the content'

def buffer(self, cdata, size=(-1)):

    return self._backend.buffer(cdata, size)
