def _construct_SAX_chunk_dict(self, sax):
frequency = defaultdict(int)<EOL>chunk_size = self.chunk_size<EOL>length = len(sax)<EOL>for i in range(length):<EOL><INDENT>if i + chunk_size <= length:<EOL><INDENT>chunk = sax[i: i + chunk_size]<EOL>frequency[chunk] += <NUM_LIT:1><EOL><DEDENT><DEDENT>return frequency<EOL>
Form a chunk frequency dictionary from a SAX representation.
:param str sax: a SAX representation.
:return dict: frequency dictionary for chunks in the SAX representation.