class Tilt::Template

argument string will be used when defining the template method if given.
surrounded by parentheses if there are fixed locals. The method
if there are no fixed locals specified, or a method argument string
Extract fixed locals from the template code string. Should return nil

def extract_fixed_locals
  if @data.is_a?(String) && (match = /\#\s*locals:\s*(\(.*\))/.match(@data))
    match[1]
  end
end