code: private void validateAsMongoDBFieldName(String fieldName) {
  		if ( fieldName.startsWith( "$" ) ) {
  			throw log.fieldNameHasInvalidDollarPrefix( fieldName );
  		}
  		else if ( fieldName.contains( "\u0000" ) ) {
  			throw log.fieldNameContainsNULCharacter( fieldName );
  		}
  	}
docs: Validates a String to be a valid name to be used in MongoDB for a field name.
  
  @param fieldName