code: def parse_body_arguments(
      content_type: str,
      body: bytes,
      arguments: Dict[str, List[bytes]],
      files: Dict[str, List[HTTPFile]],
      headers: HTTPHeaders = None,
  ) -> None:
      
      if content_type.startswith("application/x-www-form-urlencoded"):
          if headers and "Content-Encoding" in headers:
              gen_log.warning(
                  "Unsupported Content-Encoding: %s", headers["Content-Encoding"]
              )
              return
          try:
              uri_arguments = parse_qs_bytes(native_str(body), keep_blank_values=True)
          except Exception as e:
              gen_log.warning("Invalid x-www-form-urlencoded body: %s", e)
              uri_arguments = {}
          for name, values in uri_arguments.items():
              if values:
                  arguments.setdefault(name, []).extend(values)
      elif content_type.startswith("multipart/form-data"):
          if headers and "Content-Encoding" in headers:
              gen_log.warning(
                  "Unsupported Content-Encoding: %s", headers["Content-Encoding"]
              )
              return
          try:
              fields = content_type.split(";")
              for field in fields:
                  k, sep, v = field.strip().partition("=")
                  if k == "boundary" and v:
                      parse_multipart_form_data(utf8(v), body, arguments, files)
                      break
              else:
                  raise ValueError("multipart boundary not found")
          except Exception as e:
              gen_log.warning("Invalid multipart/form-data: %s", e)
docs: Parses a form request body.
  
      Supports ``application/x-www-form-urlencoded`` and
      ``multipart/form-data``.  The ``content_type`` parameter should be
      a string and ``body`` should be a byte string.  The ``arguments``
      and ``files`` parameters are dictionaries that will be updated
      with the parsed contents.