':param file_path: the path to the file that\'s being processed
:type file_path: unicode
:return: the start time of the process that\'s processing the
specified file or None if the file is not currently being processed
:rtype: datetime'

def get_start_time(self, file_path):

    if (file_path in self._processors):
        return self._processors[file_path].start_time
    return None
