code: def check_subdomain(fqn):
      
      if type(fqn) not in [str, unicode]:
          return False
  
      if not is_subdomain(fqn):
          return False
  
      return True
docs: Verify that the given fqn is a subdomain
  
      >>> check_subdomain('a.b.c')
      True
      >>> check_subdomain(123)
      False
      >>> check_subdomain('a.b.c.d')
      False
      >>> check_subdomain('A.b.c')
      False
      >>> check_subdomain('abcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcdabcd.a.b')
      True
      >>> check_subdomain('a.abcdabcdabcdabcdabcdabcdabcdabcdabcdabcd.a')
      False
      >>> check_subdomain('a.b.cdabcdabcdabcdabcdabcdabcdabcdabcd')
      False
      >>> check_subdomain('a.b')
      False