mrjob join non unique key

Question

Using mrjob, I want to map a key of table_1: a to values of x and y from table_2 and table_3, i.e z and was shown in output. I write some code mrjob combiner not working python which gives output as

a1 x1-x2-y1
a2 y1 

But how to inner join the table_1 table_2 table_3 to get the given desired output. I refer https://gist.github.com/ewencp/7010531 for innerjoin but this may not help in this case.

Table_1:
a1 x1
a1 x2
a1 y1
a2 y1

Table_2:
y1 z1
y2 z2

Table_3:
x1 w1
x2 w2

desired output:
a1 w1-w2-z1
a2 z1