text: '''
  tree_constants.py holds constants used in defining decision trees, 
  such as column definitions.
  
  Column definitions:
      0) Split feature, -1 if leaf
      1) Split threshold
      2) Node number of this node (nodes are numbered in pre-order).
      3) Node number of left child, -1 if leaf
      4) Node number of right child, -1 if leaf
      5) Number of data points in this node
      6) Value of this node
  '''
  
  # Position constants for the fields in the tree
  FEATURE_COL = 0
  THR_COL = 1
  NODE_NUM_COL = 2
  CHILD_LEFT_COL = 3
  CHILD_RIGHT_COL = 4
  CT_COL = 5
  VAL_COL = 6
  
  # FEATURE_COL value if no split/leaf
  NO_FEATURE = -2
  
  # THR_COL value if no split/leaf
  NO_THR = -2.0
  
  # CHILD_LEFT_COL and CHILD_RIGHT_COL values if leaf (no children)
  NO_CHILD = -1
  