A lot of methods should be functions instead

In https://gitlab.idiap.ch/bob/bob.pad.face/blob/c32d6518964be59618a44adfc75c1c4469c0ab1d/bob/pad/face/preprocessor/VideoSparseCoding.py, crop_norm_face_grayscale, crop_norm_faces_grayscale, select_all_blocks, convert_frame_cont_to_grayscale_array, get_all_blocks_from_color_channel, extract_patches_from_blocks, __select_random_patches_single_list, select_random_patches, get_sparse_codes_for_patches, get_sparse_codes_for_list_of_patches, load_the_dictionaries, convert_sparse_codes_to_frame_container, comp_hist_of_sparse_codes, convert_arrays_to_frame_container, mean_std_normalize, compute_patches_mean_squared_errors, compute_mse_for_all_patches_types, and compute_mse_for_all_stacks all are functions (they do not use any state of the class, no self variable is used) and not methods.

Since I can see most of them will be useful outside this class too, please consider converting them to functions.

load_array_from_hdf5 already exists as bob.bio.base.utils.load.