<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def parse(cls, format):
 """ Parse a format string. Factory function for the Format class. :param format: The format string to parse. :returns: An instance of class Format. """


        fmt = cls()

        # Return an empty Format if format is empty
        if not format:
            return fmt

        # Initialize the state for parsing
        state = ParseState(fmt, format)

        # Loop through the format string with a state-based parser
        for idx, char in enumerate(format):
            # Some characters get ignored
            if state.check_ignore():
                continue

            if state == 'string':
                if char == '%':
                    # Handle '%%'
                    if format[idx:idx + 2] == '%%':
                        # Add one % to the string context
                        state.add_text(idx + 1, idx + 2)
                        state.set_ignore(1)
                    else:
                        state.add_text(idx)
                        state.conversion(idx)
                elif char == '\\':
                    state.add_text(idx)
                    state.escape(idx)
            elif state == 'escape':
                state.add_escape(idx + 1, char)
                state.pop_state(idx + 1)
            elif state == 'param':
                if char == '}':
                    state.set_param(idx)
                    state.pop_state()
            elif state == 'conv':
                if char == ')':
                    state.set_conversion(idx)
                    state.pop_state()  # now in 'conversion'
                    state.pop_state(idx + 1)  # now in 'string'
            else:  # state == 'conversion'
                if char in '<>':
                    # Allowed for Apache compatibility, but ignored
                    continue
                elif char == '!':
                    state.set_reject()
                    continue
                elif char == ',' and state.code_last:
                    # Syntactically allowed ','
                    continue
                elif char.isdigit():
                    # True if the code is valid
                    if state.set_code(idx):
                        continue
                elif char == '{' and state.param_begin is None:
                    state.param(idx + 1)
                    continue
                elif char == '(' and state.conv_begin is None:
                    state.conv(idx + 1)
                    continue

                # OK, we have a complete conversion
                state.set_conversion(idx)
                state.pop_state(idx + 1)

        # Finish the parse and return the completed format
        return state.end_state()