class_docstr: Generic matlab matrix writing class 
code: def write_regular_element(self, arr, mdtype, byte_count):
      # write tag, data
      tag = np.zeros((), NDT_TAG_FULL)
      tag["mdtype"] = mdtype
      tag["byte_count"] = byte_count
      self.write_bytes(tag)
      self.write_bytes(arr)
      # pad to next 64-bit boundary
      bc_mod_8 = byte_count % 8
      if bc_mod_8:
          self.file_stream.write(b"\x00" * (8 - bc_mod_8))
  
imports: import os
  import time
  import sys
  import zlib
  from io import BytesIO
  import warnings
  import numpy
  import scipy.sparse
  from .byteordercodes import native_code, swapped_code
  from .miobase import MatFileReader, docfiller, matdims, read_dtype, arr_to_chars, arr_dtype_number, MatWriteError, MatReadError, MatReadWarning
  from .mio5_utils import VarReader5
  from .mio5_params import MatlabObject, MatlabFunction, MDTYPES, NP_TO_MTYPES, NP_TO_MXTYPES, miCOMPRESSED, miMATRIX, miINT8, miUTF8, miUINT32, mxCELL_CLASS, mxSTRUCT_CLASS, mxOBJECT_CLASS, mxCHAR_CLASS, mxSPARSE_CLASS, mxDOUBLE_CLASS, mclass_info, mat_struct
  from .streams import ZlibInputStream
label_desc: Use image node_id 6 for calling the VarWriter5 obj's underlying member method code with example usage: obj.write_regular_element(arr, mdtype, byte_count) without return types