code: public void setPrefix(@Nonnull String prefixName, @Nonnull String prefix) {
          if (!isUsingDefaultShortFormProvider()) {
              resetShortFormProvider();
          }
          ((DefaultPrefixManager) shortFormProvider).setPrefix(prefixName, prefix);
      }
docs: Sets a prefix name for a given prefix. Note that prefix names MUST end
  with a colon.
  
  @param prefixName
  The prefix name (ending with a colon)
  @param prefix
  The prefix that the prefix name maps to