code: public void setVariable(String variableName, Object value, boolean fetchAllVariables) {
      setVariable(variableName, value, getSourceActivityExecution(), fetchAllVariables);
    }
docs: The default {@link #setVariable(String, Object)} fetches all variables
  (for historical and backwards compatible reasons) while setting the variables.
  
  Setting the fetchAllVariables parameter to true is the default behaviour
  (ie fetching all variables) Setting the fetchAllVariables parameter to false does not do that.