def __init__(self, coordinates0, coordinates1, cutoff, unit_cell=None, grid=None):
self.cutoff = cutoff<EOL>self.unit_cell = unit_cell<EOL>grid_cell, integer_cell = self._setup_grid(cutoff, unit_cell, grid)<EOL>self.bins0 = Binning(coordinates0, cutoff, grid_cell, integer_cell)<EOL>self.bins1 = Binning(coordinates1, cutoff, grid_cell, integer_cell)<EOL>
Arguments:
 | ``coordinates0``  --  A Nx3 numpy array with Cartesian coordinates
 | ``coordinates1``  --  A Nx3 numpy array with Cartesian coordinates
 | ``radius``  --  The cutoff radius for the pair distances.
                   Distances larger than the cutoff will be neglected
                   in the pair search.

Optional arguments:
 | ``unit_cell``  --  Specifies the periodic boundary conditions
 | ``grid``  --  Specification of the grid, can be a floating point
             number which will result in cubic bins with edge length
             equal to the given number. Otherwise a UnitCell object
             can be specified to construct non-cubic bins. In the
             latter case and when a unit_cell is given, the unit cell
             vectors must be integer linear combinations of the grid
             cell vectors (for those directions that are active in
             the unit cell). If this is not the case, a ValueError is
             raised.

The default value of grid depends on other parameters:
  1) When no unit cell is given, it is equal to cutoff/2.9.
  2) When a unit cell is given, the grid cell is as close to cubic
     as possible, with spacings below cutoff/2 that are integer
     divisions of the unit cell spacings