nce the substitution is computed, the substitution should satisfy

 \sigma T = t

 where T is the Term from which the substitution is computed, and t is the term_t which results from the Prolog
 query.
 <p>

 A second Map, vars_to_Vars, is required: this table holds the Variables that occur (thus far) in the unified term.
        The Variable instances in this table are guaranteed to be unique and are keyed on Strings which are Prolog internal
 representations of the variables.</div>
<dl>
<dt><span class="p