code: def extract_literal(templatevar):
      
      # FilterExpression contains another 'var' that either contains a Variable or SafeData object.
      if hasattr(templatevar, 'var'):
          templatevar = templatevar.var
          if isinstance(templatevar, SafeData):
              # Literal in FilterExpression, can return.
              return templatevar
          else:
              # Variable in FilterExpression, not going to work here.
              return None
  
      if templatevar[0] in ('"', "'") and templatevar[-1] in ('"', "'"):
          return templatevar[1:-1]
      else:
          return None
docs: See if a template FilterExpression holds a literal value.
  
      :type templatevar: django.template.FilterExpression
      :rtype: bool|None