def __init__(self, **cfg):
self.node_names = cfg["<STR_LIT>"]<EOL>self.field_names = cfg.get("<STR_LIT>", {})<EOL>
Initialize speaker instance, for a set of AST nodes.

        Arguments:
            nodes:  dictionary of node names, and their human friendly names.
                    Each entry for a node may also be a dictionary containing
                    name: human friendly name, fields: a dictionary to override
                    the field names for that node.
            fields: dictionary of human friendly field names, used as a default
                    for each node.