def taxonomy_from_node_name(self, node_name):
def is_float(s):<EOL><INDENT>try:<EOL><INDENT>float(s)<EOL>return True<EOL><DEDENT>except ValueError:<EOL><INDENT>return False<EOL><DEDENT><DEDENT>if node_name is None:<EOL><INDENT>return None<EOL><DEDENT>elif is_float(node_name):<EOL><INDENT>return None<EOL><DEDENT>else:<EOL><INDENT>bootstrap_regex = re.compile(r'<STR_LIT>')<EOL>reg = bootstrap_regex.match(node_name)<EOL>if reg:<EOL><INDENT>return reg.groups(<NUM_LIT:0>)[<NUM_LIT:0>]<EOL><DEDENT>else:<EOL><INDENT>return node_name<EOL><DEDENT><DEDENT>
return the taxonomy incorporated at a particular node, or None
        if it does not encode any taxonomy

        Parameters
        ----------
        node_name: str
            a node label.

        Returns
        -------
        Taxonomy as a string, or None if there is no taxonomy