The function get_min_index in the hana_ml.visualizers.m4_sampling module returns the minimum 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_min_index` function:

```python
# Import necessary libraries
from hana_ml.visualizers import m4_sampling
from datetime import datetime


# Use the get_min_index function
min_timestamp = m4_sampling.get_min_index(data)

# Print the result
print(min_timestamp)
```

Please replace the `data` DataFrame with your actual time series data. The `get_min_index` function will return the minimum timestamp in the 'index' column of your DataFrame.