v3.20.0

• Breaking Change: The Cell.value property no longer automatically clears the cell's style when a new value is set. Previously, setting Cell.value would remove existing styling, and other properties like cell span, xml:id .... Now, styling and other properties are preserved. If the old behavior of clearing styles is desired, explicitly call Cell.clear() before setting the new value (issue #63).
• Enhanced element manipulation with Element.del_attribute_list() and ElementTyped.clear_attributes() methods.