retuen the phone number of the sender concode_field_sep Map<String,Object> properties concode_elem_sep int OUT_MESSAGE concode_elem_sep String receiver concode_elem_sep String sender concode_elem_sep int IN_MESSAGE concode_elem_sep String content concode_elem_sep int direction concode_field_sep String getReceiver concode_elem_sep int getDirection concode_elem_sep String getContent concode_elem_sep Map<String,Object> getProperties concode_elem_sep void addProperty