def generate_docstring(operation_spec):
    """Generate a docstring for an operation defined in operation_spec (swagger)"""
    docs = operation_spec.get('description', 'No Description')
    docs += '\n\n'
    parameters = operation_spec.get('parameters', [])
    if len(parameters) != 0:
        docs += '\tArguments:\n\n'
    for parameter in parameters:
        docs += '{0} ({1}:{2}): {3}\n'.format(parameter.get('name'),
            parameter.get('type', 'No Type'), 'Required' if parameter.get(
            'required', False) else 'Not Required', parameter.get(
            'description'))
    return docs
