remove useless argument in word hashing unnit

matchzoo/preprocessor/process_units.py

@@ -317,8 +317,7 @@ class WordHashingUnit(ProcessorUnit):
     Examples:
        >>> tri_letters = ['#te', 'tes','est', 'st#']
        >>> word_hashing = WordHashingUnit(
-       ...     term_index={'': 0,'st#': 1, '#te': 2, 'est': 3, 'tes': 4},
-       ...     dim_triletter=5)
+       ...     term_index={'': 0,'st#': 1, '#te': 2, 'est': 3, 'tes': 4})
        >>> hashing = word_hashing.transform(tri_letters)
        >>> hashing[0]
        0.0
@@ -332,30 +331,28 @@ class WordHashingUnit(ProcessorUnit):
     def __init__(
         self,
         term_index: dict,
-        dim_triletter: int
     ):
         """
         Class initialization.
 
         :param term_index: term-index mapping generated by
-        :class:`VocabularyUnit`.
+                           :class:`VocabularyUnit`.
         :param dim_triletter: dimensionality of tri_leltters.
         """
         self._term_index = term_index
-        self._dim_triletter = dim_triletter
 
     def transform(
         self,
         tri_letters: list
     ) -> np.ndarray:
         """
-        Transform list of tri-letters into word hashing layer.
+        Transform list of :attr:`tri-letters` into word hashing layer.
 
         :param tri_letters: list of `tri_letters` generated by
         :class:`NgramLetterUnit`.
         :return: Word hashing representation of `tri-letters`.
         """
-        hashing = np.zeros(self._dim_triletter)
+        hashing = np.zeros(len(self._term_index))
         counted_tri_letters = dict(collections.Counter(tri_letters))
         for key, value in counted_tri_letters.items():
             # get index.