public static TensorType fromSpec(String specString) {
        return TensorTypeParser.fromSpec(specString);
    }
Returns a tensor type instance from a
<a href="https://docs.vespa.ai/en/reference/tensor.html#tensor-type-spec">tensor type spec</a>:
<code>tensor(dimension1, dimension2, ...)</code>
where each dimension is either
<ul>
    <li><code>dimension-name[]</code> - an unbound indexed dimension
    <li><code>dimension-name[int]</code> - an bound indexed dimension
    <li><code>dimension-name{}</code> - a mapped dimension
</ul>
Example: <code>tensor(x[10],y[20])</code> (a matrix)
vespajlib/src/main/java/com/yahoo/tensor/TensorType.java