whole_func_string: function getAcceptedLanguagesFromHeader( header ) {
  	if ( ! header ) {
  		return [];
  	}
  
  	return header
  		.split( ',' )
  		.map( lang => {
  			const match = lang.match( /^[A-Z]{2,3}(-[A-Z]{2,3})?/i );
  			if ( ! match ) {
  				return false;
  			}
  
  			return match[ 0 ].toLowerCase();
  		} )
  		.filter( lang => lang );
  }
func_code_string: function getAcceptedLanguagesFromHeader( header ) {
  	if ( ! header ) {
  		return [];
  	}
  
  	return header
  		.split( ',' )
  		.map( lang => {
  			const match = lang.match( /^[A-Z]{2,3}(-[A-Z]{2,3})?/i );
  			if ( ! match ) {
  				return false;
  			}
  
  			return match[ 0 ].toLowerCase();
  		} )
  		.filter( lang => lang );
  }
func_documentation_string: Given the content of an 'Accept-Language' request header, returns an array of the languages.
  
  This differs slightly from other language functions, as it doesn't try to validate the language codes,
  or merge similar language codes.
  
  @param  {string} header - The content of the AcceptedLanguages header.
  @return {Array} An array of language codes in the header, all in lowercase.