def add_child_hash(self, child_hash, permute_config):
<EOL>if not (isinstance(child_hash,PCABinaryProjections) or isinstance(child_hash,RandomBinaryProjections) or isinstance(child_hash,RandomBinaryProjectionTree)):<EOL><INDENT>raise ValueError('<STR_LIT>')<EOL><DEDENT>self.child_hashes.append({'<STR_LIT>': child_hash, '<STR_LIT>': permute_config, '<STR_LIT>': {}})<EOL>
Adds specified child hash with specified configuration.
The hash must be one of the binary types.

permute_config is a dict in the following format:
permute_config = { "num_permutation":50,
                   "beam_size":10,
                   "num_neighbour":100
                 }