def find_supply(suppliers,parts,sno,pno):
  #1 check if sno is present in suppliers
  found_s, pos_s = suppliers.find(sno)
  if not found_s:
    return (False,None,....)
  else:
    #2 check is pno is present in parts
    found_p, pos_p = parts.find(pno)
    if not found_p:
        return (False,None,....)
    else:
      #3 check if sno-pno is present in "supply"
      # check in supply list originating from supplier node (pos_s.get_next().get_first_supply())
        ... use snext
       
        return (True,sp,)
 
        return (False,sp,)
      # check in supply list originating from part node (pos_p.get_next().get_first_supply())
        ... use pnext
 
        return (True,sp,....)
 
        return (False,sp,.....)
 
    #return (True,sp,ps,found_s,pos_s,found_p,pos_p)
 
    #return (False,sp,ps,found_s,pos_s,found_p,pos_p)