>>> m.fit(input_fn = train_input_fn,steps=200)  

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

  File "/usr/lib/python2.7/site-packages/tensorflow/python/util/deprecation.py", line 281, in new_func

    return func(*args, **kwargs)

  File "/usr/lib/python2.7/site-packages/tensorflow/contrib/learn/python/learn/estimators/estimator.py", line 430, in fit

    loss = self._train_model(input_fn=input_fn, hooks=hooks)

  File "/usr/lib/python2.7/site-packages/tensorflow/contrib/learn/python/learn/estimators/estimator.py", line 927, in _train_model

    model_fn_ops = self._get_train_ops(features, labels)

  File "/usr/lib/python2.7/site-packages/tensorflow/contrib/learn/python/learn/estimators/estimator.py", line 1132, in _get_train_ops

    return self._call_model_fn(features, labels, model_fn_lib.ModeKeys.TRAIN)

  File "/usr/lib/python2.7/site-packages/tensorflow/contrib/learn/python/learn/estimators/estimator.py", line 1103, in _call_model_fn

    model_fn_results = self._model_fn(features, labels, **kwargs)

  File "/usr/lib/python2.7/site-packages/tensorflow/contrib/learn/python/learn/estimators/dnn_linear_combined.py", line 222, in _dnn_linear_combined_model_fn

    scope=dnn_input_scope)

  File "/usr/lib/python2.7/site-packages/tensorflow/contrib/layers/python/layers/feature_column_ops.py", line 249, in input_from_feature_columns

    default_name='input_from_feature_columns')

  File "/usr/lib/python2.7/site-packages/tensorflow/contrib/layers/python/layers/feature_column_ops.py", line 147, in _input_from_feature_columns

    check_feature_columns(feature_columns)

  File "/usr/lib/python2.7/site-packages/tensorflow/contrib/layers/python/layers/feature_column_ops.py", line 811, in check_feature_columns

    key = f.key

AttributeError: 'str' object has no attribute 'key'

老师，我在train的时候报错：AttributeError: 'str' object has no attribute 'key'，代码用老师提供的train数据就没问题，我用我自己的数据跑的时候就报错，我的数据类型只有float和int两种类型，请问老师这个是啥原因导致的