class Gherkin::TokenScanner

in gherkin-languages.json.
to look for Gherkin keywords for the associated language. The keywords are defined
If the scanner sees a # language header, it will reconfigure itself dynamically
an AST (Abstract Syntax Tree).
creates a token for line. The tokens are passed to the parser, which outputs
The scanner reads a gherkin doc (typically read from a .feature file) and

def initialize(source_or_io) 

def initialize(source_or_io)
  @line_number = 0
  case(source_or_io)
  when String
    @io = StringIO.new(source_or_io)
  when StringIO, IO
    @io = source_or_io
  else
    fail ArgumentError, "Please a pass String, StringIO or IO. I got a #{source_or_io.class}"
  end
end

def read 

def read
  location = {line: @line_number += 1, column: 0}
  if @io.nil? || line = @io.gets
    gherkin_line = line ? GherkinLine.new(line, location[:line]) : nil
    Token.new(gherkin_line, location)
  else
    @io.close unless @io.closed? # ARGF closes the last file after final gets
    @io = nil
    Token.new(nil, location)
  end
end