code: static public IVariableAssigner setInstance(final IVariableAssigner newInstance)
      {
          final IVariableAssigner previousAssigner = instance;
          instance = newInstance;
          return previousAssigner;
      }
docs: <p>
  Setter for the field <code>instance</code>.
  </p>
  
  @param newInstance a
  {@link com.obdobion.argument.variables.IVariableAssigner}
  object.
  @return a {@link com.obdobion.argument.variables.IVariableAssigner}
  object.