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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 is_valid_method(model, resource=None):
 """Return the error message to be sent to the client if the current request passes fails any user-defined validation."""

    validation_function_name = 'is_valid_{}'.format(
        request.method.lower())
    if hasattr(model, validation_function_name):
        return getattr(model, validation_function_name)(request, resource)