Returns a dictionary of coordination numbers for each site type.

        Args:
            None

        Returns:
            (Dict(Str:List(Int))) : Dictionary of coordination numbers for each site type, e.g.::

                { 'A' : [ 2, 4 ], 'B' : [ 2 ] }

def site_specific_coordination_numbers( self ):
        """
        Returns a dictionary of coordination numbers for each site type.

        Args:
            None

        Returns:
            (Dict(Str:List(Int))) : Dictionary of coordination numbers for each site type, e.g.::

                { 'A' : [ 2, 4 ], 'B' : [ 2 ] }
        """
        specific_coordination_numbers = {}
        for site in self.sites:
            specific_coordination_numbers[ site.label ] = site.site_specific_neighbours()
        return specific_coordination_numbers