old_contents: NON_POSITIVE_NUM_MESSAGE = "the segment size should be larger than zero"
  NEG_NUM_MESSAGE = "the overlap or last segment proportion should " \
      "not be negative"
  LARGER_CHUNK_SIZE_MESSAGE = "the segment size should be larger " \
      "than the overlap size"
  NON_POSITIVE_INDEX_MESSAGE = "the index should be larger than or equal to zero"
  MATRIX_DIMENSION_UNEQUAL_MESSAGE = "the dimension of the matrix " \
      "should be equal"
  
new_contents: NON_POSITIVE_NUM_MESSAGE = "the segment size should be larger than zero"
  NEG_NUM_MESSAGE = "the overlap or last segment proportion should " \
      "not be negative"
  LARGER_CHUNK_SIZE_MESSAGE = "the segment size should be larger " \
      "than the overlap size"
  NON_POSITIVE_INDEX_MESSAGE = "the index should be larger than or equal to zero"
  MATRIX_DIMENSION_UNEQUAL_MESSAGE = "the dimension of the matrix " \
      "should be equal"
  EMPTY_LIST_MESSAGE = "the list should not be empty"
  
subject: add one error message