class_docstr: Translates the text of tokens by calling unicode.translate() using the
  supplied character mapping object. This is useful for case and accent
  folding.
  
  The ``whoosh.support.charset`` module has a useful map for accent folding.
  
  >>> from whoosh.support.charset import accent_map
  >>> retokenizer = RegexTokenizer()
  >>> chfilter = CharsetFilter(accent_map)
  >>> [t.text for t in chfilter(retokenizer(u'café'))]
  [u'cafe']
  
  Another way to get a character mapping object is to convert a Sphinx
  charset table file using
  :func:`whoosh.support.charset.charset_table_to_dict`.
  
  >>> from whoosh.support.charset import charset_table_to_dict
  >>> from whoosh.support.charset import default_charset
  >>> retokenizer = RegexTokenizer()
  >>> charmap = charset_table_to_dict(default_charset)
  >>> chfilter = CharsetFilter(charmap)
  >>> [t.text for t in chfilter(retokenizer(u'Stra\xdfe'))]
  [u'strase']
  
  The Sphinx charset table format is described at
  http://www.sphinxsearch.com/docs/current.html#conf-charset-table.
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code: def __call__(self, tokens):
      assert hasattr(tokens, "__iter__")
      charmap = self.charmap
      for t in tokens:
          t.text = t.text.translate(charmap)
          yield t
  
imports: from itertools import chain
  from whoosh.compat import next
  from whoosh.analysis.acore import Composable
  from whoosh.util.text import rcompile
label_desc: Use image node_id 3 for calling the CharsetFilter obj's underlying member method code with example usage: obj.__call__(tokens) without return types