def add(file, line, expression = nil)
      real_file = (file != Pry.eval_path)
      raise ArgumentError, 'Invalid file!' if real_file && !File.exist?(file)
      validate_expression expression

      Pry.processor.debugging = true

      path = (real_file ? File.expand_path(file) : file)
      Debugger.add_breakpoint(path, line, expression)
    end
def add(file, line, expression = nil)
      real_file = (file != Pry.eval_path)
      raise ArgumentError, 'Invalid file!' if real_file && !File.exist?(file)
      validate_expression expression

      Pry.processor.debugging = true

      path = (real_file ? File.expand_path(file) : file)
      Debugger.add_breakpoint(path, line, expression)
    end
Add a new breakpoint.