def installed?(package)
      fail LookupFailed, 'No supported package tool found.' if tool.nil?

      cmd = tools[tool]
      fail LookupFailed, "Package tool '#{cmd}' not found." if command?(cmd).nil?

      send tool, package
    end
def installed?(package)
      fail LookupFailed, 'No supported package tool found.' if tool.nil?

      cmd = tools[tool]
      fail LookupFailed, "Package tool '#{cmd}' not found." if command?(cmd).nil?

      send tool, package
    end
Checks if package is installed.
 @param package [String] package name to check
 @return [Boolean] if package is installed