Return boolean type user input

def get_boolean(self, input_string):
        """
		Return boolean type user input
		"""

        if input_string in ('--write_roc', '--plot', '--compare'):

            # was the flag set?
            try:
                index = self.args.index(input_string) + 1
            except ValueError:
                # it wasn't, args are optional, so return the appropriate default
                return False

            # the flag was set, so return the True
            return True