### Example: mark empty

| tree_node_nts |
SYM | "S"
FUNC | nil
HEAD_MARK | non_empty
ID | nil
SCHEMA_NAME | bot
PROP_LIST | prop_nil
NODE_SIGN | bot
ANNOT | bot
| tree_node_nts |
SYM | "NP"
FUNC |
< | "SBJ" | >
HEAD_MARK | non_empty
ID | nil
SCHEMA_NAME | bot
PROP_LIST | prop_nil
NODE_SIGN | bot
ANNOT | bot
| tree_node_term |
SYM | "NNP"
FUNC | nil
HEAD_MARK | non_empty
WORD |
| word |
INPUT | "Ms."
SURFACE | "ms-period-"
BASE | string
INPUT_POS | 1"NNP"
POS | 1
BASE_POS | string
POSITION | 0
PROP_LIST | prop_nil
NODE_SIGN | bot
ANNOT | bot
| tree_node_term |
SYM | "NNP"
FUNC | nil
HEAD_MARK | non_empty
WORD |
| word |
INPUT | "Haag"
SURFACE | "haag"
BASE | string
INPUT_POS | 2"NNP"
POS | 2
BASE_POS | string
POSITION | 1
PROP_LIST | prop_nil
NODE_SIGN | bot
ANNOT | bot
| tree_node_nts |
SYM | "VP"
FUNC | nil
HEAD_MARK | non_empty
ID | nil
SCHEMA_NAME | bot
PROP_LIST | prop_nil
NODE_SIGN | bot
ANNOT | bot
| tree_node_term |
SYM | "VBZ"
FUNC | nil
HEAD_MARK | non_empty
WORD |
| word |
INPUT | "plays"
SURFACE | "plays"
BASE | string
INPUT_POS | 3"VBZ"
POS | 3
BASE_POS | string
POSITION | 2
PROP_LIST | prop_nil
NODE_SIGN | bot
ANNOT | bot
| tree_node_nts |
SYM | "NP"
FUNC | nil
HEAD_MARK | non_empty
ID | nil
SCHEMA_NAME | bot
PROP_LIST | prop_nil
NODE_SIGN | bot
ANNOT | bot
| tree_node_term |
SYM | "NNP"
FUNC | nil
HEAD_MARK | non_empty
WORD |
| word |
INPUT | "Elianti"
SURFACE | "elianti"
BASE | string
INPUT_POS | 4"NNP"
POS | 4
BASE_POS | string
POSITION | 3
PROP_LIST | prop_nil
NODE_SIGN | bot
ANNOT | bot