python 2.7 : find nested keys in dictionary : I have several dictionaries , dictionary keys are tupples.

Keys are always same length in each dictionary.  

I'd like to find nested keys and print them .

dictionaries example :

    dic_1 =
    {
     (u'A_String', u'B_String', u'C_String', u'D_String', u'E_String'): 111, 
     (u'A_String', u'B_String', u'C_String', u'D_String' ,u'F_String'): 112
    }


     dic_2 = 
    {
     (u'A_String', u'B_String', u'C_String', u'D_String'): 300, 
     (u'A_String', u'B_String', u'C_String', u'F_String'): 301,
     }


    dic_3 = 
    {
     (u'A_String', u'B_String', u'C_String'): 200, 
     (u'A_String', u'B_String', u'F_String'): 201,
    }

First row in dic_3 is nested in first row in dic_2 and dic_1

First row in dic_2 is nested in first row of dic_1 

I tried  :
  
    for key in dic_1:
    print '-',key
    for k in dic_2:
        if k in tuple(key):
            print '--', k
            for i in dic_3:
                if i in tuple(k):
                    print '---', i

Thank you in advance !
