The function get_max_index in module hana_ml.visualizers.m4_sampling retrieves the maximum timestamp from the time series data provided in the DataFrame, where the first column is the index and the second one is the value.
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Here is a Python code template for the `get_max_index` function:

```python
# Import necessary modules
from hana_ml.visualizers import m4_sampling

# Convert 'index' column to datetime
data['index'] = pd.to_datetime(data['index'])

# Use the get_max_index function
max_timestamp = m4_sampling.get_max_index(data)

# Print the maximum timestamp
print(max_timestamp)
```

Please replace the DataFrame `data` with your actual time series data. The 'index' column should be of datetime type. The `get_max_index` function will return the maximum timestamp in the 'index' column.