Python!Create a function dict_agg that takes two dictionaries, where all values are str/ints/floats, and sums values based on the key.

Ex. {a : hello, b : 4, c : 8}, { b : 2, c : four} -> {b : 6, c : 8}

Note: 'a' does not exist in the output, as it does not have any numeric values associated with it.