code: static ColumnSpec decodeExpanded(String expandedTrimmedLowerCaseSpec) {
          ColumnSpec spec = CACHE.get(expandedTrimmedLowerCaseSpec);
          if (spec == null) {
              spec = new ColumnSpec(expandedTrimmedLowerCaseSpec);
              CACHE.put(expandedTrimmedLowerCaseSpec, spec);
          }
          return spec;
      }
docs: Decodes an expanded, trimmed, lower case column spec. Called by the public ColumnSpec factory
  methods. Looks up and returns the ColumnSpec object from the cache - if any, or constructs
  and returns a new ColumnSpec instance.
  
  @param expandedTrimmedLowerCaseSpec the encoded column specification
  @return a ColumnSpec for the given encoded column spec