You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: backtracefilter.rb
    path of file: ./repos/ruby-packer/ruby/gems/test-unit-3.3.4/lib/test/unit/util
    
    the code of the file until where you have to start completion: begin
  require 'power_assert'
rescue LoadError, SyntaxError
end

module Test
  module Unit
    module Util
      module BacktraceFilter
        TESTUNIT_FILE_SEPAR
    
        def filter_backtrace(backtrace, prefix=nil)
          return ["No backtrace"] unless backtrace
          return backtrace if ENV["TEST_UNIT_ALL_BACKTRACE"]

          if prefix
            split_prefixes = [prefix.split(TESTUNIT_FILE_SEPARATORS)]
          else
            split_prefixes = [TESTUNIT_PREFIX, POWERASSERT_PREFIX].compact
          end