code: public void setFunction(String name, Operation function, Template template,
  			SourceRange sourceRange) throws EvaluationException {
  		// Should never be called.
  	}
docs: Define the given DML block as a function with the given name in this
  context. Note that functions may not be redefined; attempting to do so
  will throw an EvaluationException.
  
  @param name
  name for the function
  @param function
  code for the function as a DML block
  @param template
  template in which this function is defined (used for error
  handling)
  @param sourceRange
  location in the template where this function is defined (used
  for error handling)
  
  @throws EvaluationException
  if a function with the given name already exists