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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def in_cwd():
 """ Return list of configs in current working directory. If filename is ``.tmuxp.py``, ``.tmuxp.json``, ``.tmuxp.yaml``. Returns ------- list configs in current working directory """

    configs = []

    for filename in os.listdir(os.getcwd()):
        if filename.startswith('.tmuxp') and is_config_file(filename):
            configs.append(filename)

    return configs