'aux_trans : a transform from the source (curved) coordinate to
target (rectilinear) coordinate. An instance of MPL\'s Transform
(inverse transform should be defined) or a tuple of two callable
objects which defines the transform and its inverse. The callables
need take two arguments of array of source coordinates and
should return two target coordinates.
e.g., ``x2, y2 = trans(x1, y1)``'

def __init__(self, aux_trans, extreme_finder=None, grid_locator1=None, grid_locator2=None, tick_formatter1=None, tick_formatter2=None):

    super(GridHelperCurveLinear, self).__init__()
    self.grid_info = None
    self._old_values = None
    self._aux_trans = aux_trans
    self.grid_finder = GridFinder(aux_trans, extreme_finder, grid_locator1, grid_locator2, tick_formatter1, tick_formatter2)
