读取csv文件时，Kaggle中出现错误消息

Question

data = pd.read_csv('/kaggle/input/covidtracking/all-states-history.csv', index_col=0, parse_dates=True)
data.shape

/opt/conda/lib/python3.7/site-packages/IPython/core/interactiveshell.py:3063: 
DtypeWarning: Columns (2) have mixed types.
Specify dtype option on import or set low_memory=False.
  interactivity=interactivity, compiler=compiler, result=result)
(16931, 41)

第（2）列有质量评级元素，其值为A、A+、B、B+等

在CSV文件中，每列上方列出的数据类型为“标准”