'Document accessor cache contructor. Will cache fetchsize style info
pieces starting from position - 1.
@param accessor {Accessor} a form of document accessor
@param position {int} where in the document to start caching from (exclusive)
@param fetchsize {int} how much cache is stored/retrived at a time'

def __init__(self, accessor, position, fetchsize=20, debug=False):

    self._accessor = accessor
    self._cachefetchsize = fetchsize
    self._debug = debug
    self._reset(position)
