class_docstr: MERSI-2/MERSI-LL L1B file reader.
docstr: Time for first observation.
docstr_tok: ["Time","for","first","observation","."]
code: def start_time(self):
      """Time for first observation."""
      return self._strptime(
          "/attr/Observing Beginning Date",
          "/attr/Observing Beginning Time",
      )
  
file_path: satpy/satpy/readers/mersi_l1b.py
imports: from datetime import datetime
  import dask.array
  import numpy
  from pyspectral.blackbody import blackbody_wn_rad2temp
  from satpy.readers.hdf5_utils import HDF5FileHandler
label_desc: Use image node_id 2 for calling the MERSIL1B obj's underlying member method code with example usage: obj.start_time() and returns: self