class Capybara::Selector::CSS

def self.escape(str)
  value = str.dup
  out = +''
  out << value.slice!(0...1) if value =~ /^[-_]/
  out << (value[0] =~ NMSTART ? value.slice!(0...1) : escape_char(value.slice!(0...1)))
  out << value.gsub(/[^a-zA-Z0-9_-]/) { |char| escape_char char }
  out
end