Returns a dictionary of the maximum coordination number for each site label.
        e.g.::
   
            { 'A' : 4, 'B' : 4 }

        Args:
            none

        Returns:
            max_coordination_numbers (Dict(Str:Int)): dictionary of maxmimum coordination
                                                      number for each site label.

def max_site_coordination_numbers( self ):
        """
        Returns a dictionary of the maximum coordination number for each site label.
        e.g.::
   
            { 'A' : 4, 'B' : 4 }

        Args:
            none

        Returns:
            max_coordination_numbers (Dict(Str:Int)): dictionary of maxmimum coordination
                                                      number for each site label.
        """
        return { l : max( c ) for l, c in self.site_coordination_numbers().items() }