anchor.diff:  
   *Return Type*: [.returnType]#Boolean#
   
  -*Examples*: `${filename:notNull()}` returns `true` if the "filename" attribute exists. It returns "false" if the attribute
  +*Examples*: `${filename:notNull()}` returns `true` if the "filename" attribute exists. It returns `false` if the attribute
   	does not exist.
   
   
  
positive.code: *Return Type*: [.returnType]#Boolean#
  
  *Examples*:	`${filename:isNull()}` returns `true` if the "filename" attribute does not exist. 
  	It returns `true` if the attribute exists.
  
  
  
  
negative.code: 
  	- [.argName]#_value_# : [.argDesc]#The String to search for in the Subject#
  
  *Return Type*: [.returnType]#String#
  
  *Examples*: If the "filename" attribute has the value "a brand new filename.txt",
  	then the following Expressions will result in the following values:
  