':return: the given file(s) as a single string.
:rtype: str'

def raw(self, fileids=None):

    if (fileids is None):
        fileids = self._fileids
    elif isinstance(fileids, string_types):
        fileids = [fileids]
    raw_texts = []
    for f in fileids:
        _fin = self.open(f)
        raw_texts.append(_fin.read())
        _fin.close()
    return concat(raw_texts)
