def __init__(self):
self.case_sensitive = False<EOL>self._values = {}<EOL>self.classifiers = []<EOL>
Hierarchical tree of words classified by semantic type.
            For example: "rose" and "daffodil" can be classified as "flower":
            >>> taxonomy.append("rose", type="flower")
            >>> taxonomy.append("daffodil", type="flower")
            >>> print(taxonomy.children("flower"))
            Taxonomy terms can be used in a Pattern:
            FLOWER will match "flower" as well as "rose" and "daffodil".
            The taxonomy is case insensitive by default.