docs: 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