':param label: The most likely label for tokens that reach
this node in the decision tree.  If this decision tree
has no children, then this label will be assigned to
any token that reaches this decision tree.
:param feature_name: The name of the feature that this
decision tree selects for.
:param decisions: A dictionary mapping from feature values
for the feature identified by ``feature_name`` to
child decision trees.
:param default: The child that will be used if the value of
feature ``feature_name`` does not match any of the keys in
``decisions``.  This is used when constructing binary
decision trees.'

def __init__(self, label, feature_name=None, decisions=None, default=None):

    self._label = label
    self._fname = feature_name
    self._decisions = decisions
    self._default = default
