The input dataset must yield batched 1-d tensors. This function reads each
coordinate of the tensor as an individual element and caps the total number of
elements to return. Note that the returned set of top words will not
necessarily be sorted.
A rank-1 Tensor containing the top max_user_contribution unique elements
of the input dataset. If the total number of unique words is less than or
equal to max_user_contribution, returns the list of all unique elements.