code: def _is_compress_filetype(self, inpath):
          
          # check for common file type suffixes in order to avoid the need for file reads to check magic number for binary vs. text file
          if self._is_common_binary(inpath):
              return False
          elif self._is_common_text(inpath):
              return True
          else:
              # files > 10kB get checked for compression (arbitrary decision to skip compression on small files)
              the_file_size = file_size(inpath)
              if the_file_size > 10240:
                  if the_file_size > 512000:  # seems to be a break point at ~ 500kb where file compression offset by additional file read, so limit tests to files > 500kB
                      try:
                          system_command = "file --mime-type -b " + quote(inpath)
                          response = muterun(system_command)
                          if response.stdout[0:5] == "text/":  # check for a text file mime type
                              return True   # appropriate size, appropriate file mime type
                          else:
                              return False  # appropriate size, inappropriate file mime type
                      except Exception:
                          return False
                  else:
                      return True  # if file size is < 500kB, skip the additional file read and just go with compression
              else:
                  return False
docs: private method that performs magic number and size check on file to determine whether to compress the file