def grep(self, needle):
        """
        Search all lines in file for substring 'needle'.
            equiv to: `grep "needle" ./file`

        Return matching lines as a List of Strings.
        If no matches returns False

        :param needle: String; word or phrase to search for.
        :return: List of Strings, or False.
        """
        result = []
        for line in self.contents:
            if needle in line:
                result.append(line)
        if result:
            return result
        return False
Search all lines in file for substring 'needle'.
            equiv to: `grep "needle" ./file`

        Return matching lines as a List of Strings.
        If no matches returns False

        :param needle: String; word or phrase to search for.
        :return: List of Strings, or False.