Function python3_sys::PyUnicode_CopyCharacters

pub unsafe extern "C" fn PyUnicode_CopyCharacters(
    to: *mut PyObject, 
    to_start: Py_ssize_t, 
    from: *mut PyObject, 
    from_start: Py_ssize_t, 
    how_many: Py_ssize_t
) -> Py_ssize_t