<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def format_py2js(cls, datetime_format):
 """Convert python datetime format to moment datetime format."""

        for js_format, py_format in cls.format_map:
            datetime_format = datetime_format.replace(py_format, js_format)
        return datetime_format