logical check whether a cluster connects with itself across the
        simulation periodic boundary conditions.

        Args:
            none

        Returns
            ( Bool, Bool, Bool ): Contiguity along the x, y, and z coordinate axes

def is_periodically_contiguous( self ):
        """
        logical check whether a cluster connects with itself across the
        simulation periodic boundary conditions.

        Args:
            none

        Returns
            ( Bool, Bool, Bool ): Contiguity along the x, y, and z coordinate axes
        """
        edges = self.sites_at_edges()
        is_contiguous = [ False, False, False ]
        along_x = any( [ s2 in s1.p_neighbours for s1 in edges[0] for s2 in edges[1] ] )
        along_y = any( [ s2 in s1.p_neighbours for s1 in edges[2] for s2 in edges[3] ] )
        along_z = any( [ s2 in s1.p_neighbours for s1 in edges[4] for s2 in edges[5] ] )
        return ( along_x, along_y, along_z )