Merged Cell Headers Inconsistency

[noorbuchi]

Describe the bug
When retrieving data from google sheets that contain merged cells as headers, it creates an inconsistent number of headers and columns.

To Reproduce
Using the following data:

And the following configuration:

source_id: 1jMbGVHjXs-lQbh5pstplrCOo5f76C_Nj2SOyL-bsZsQ
sheets:
    - name: Sheet1
      regions:
      - name: lab1
        start: A1
        end: E12
        contains_headers: true

This error is produced:

Traceback (most recent call last):
  File "/home/noboshe/.cache/pypoetry/virtualenvs/sheetshuttle-PeNuXww9-py3.9/lib/python3.9/site-packages/pandas/core/internals/construction.py", line 982, in _finalize_columns_and_data
    columns = _validate_or_indexify_columns(contents, columns)
  File "/home/noboshe/.cache/pypoetry/virtualenvs/sheetshuttle-PeNuXww9-py3.9/lib/python3.9/site-packages/pandas/core/internals/construction.py", line 1030, in _validate_or_indexify_columns
    raise AssertionError(
AssertionError: 2 columns passed, passed data had 5 columns

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/home/noboshe/.cache/pypoetry/virtualenvs/sheetshuttle-PeNuXww9-py3.9/lib/python3.9/site-packages/typer/main.py", line 214, in __call__
    return get_command(self)(*args, **kwargs)
  File "/home/noboshe/.cache/pypoetry/virtualenvs/sheetshuttle-PeNuXww9-py3.9/lib/python3.9/site-packages/click/core.py", line 829, in __call__
    return self.main(*args, **kwargs)
  File "/home/noboshe/.cache/pypoetry/virtualenvs/sheetshuttle-PeNuXww9-py3.9/lib/python3.9/site-packages/click/core.py", line 782, in main
    rv = self.invoke(ctx)
  File "/home/noboshe/.cache/pypoetry/virtualenvs/sheetshuttle-PeNuXww9-py3.9/lib/python3.9/site-packages/click/core.py", line 1066, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/noboshe/.cache/pypoetry/virtualenvs/sheetshuttle-PeNuXww9-py3.9/lib/python3.9/site-packages/click/core.py", line 610, in invoke
    return callback(*args, **kwargs)
  File "/home/noboshe/.cache/pypoetry/virtualenvs/sheetshuttle-PeNuXww9-py3.9/lib/python3.9/site-packages/typer/main.py", line 497, in wrapper
    return callback(**use_params)  # type: ignore
  File "/home/noboshe/SheetShuttle/SheetShuttle/sheetshuttle/main.py", line 52, in sheetshuttle
    my_plugin.run(sheets_keys_file, sheets_config_directory)
  File "/home/noboshe/SheetShuttle/SheetShuttle/../sample_plugin.py", line 8, in run
    my_collector.collect_files()
  File "/home/noboshe/SheetShuttle/SheetShuttle/sheetshuttle/sheet_collector.py", line 135, in collect_files
    sheet_obj.collect_regions()
  File "/home/noboshe/SheetShuttle/SheetShuttle/sheetshuttle/sheet_collector.py", line 204, in collect_regions
    data = Sheet.to_dataframe(region_data)
  File "/home/noboshe/SheetShuttle/SheetShuttle/sheetshuttle/sheet_collector.py", line 270, in to_dataframe
    return pd.DataFrame(data[1:], columns=data[0])
  File "/home/noboshe/.cache/pypoetry/virtualenvs/sheetshuttle-PeNuXww9-py3.9/lib/python3.9/site-packages/pandas/core/frame.py", line 721, in __init__
    arrays, columns, index = nested_data_to_arrays(
  File "/home/noboshe/.cache/pypoetry/virtualenvs/sheetshuttle-PeNuXww9-py3.9/lib/python3.9/site-packages/pandas/core/internals/construction.py", line 519, in nested_data_to_arrays
    arrays, columns = to_arrays(data, columns, dtype=dtype)
  File "/home/noboshe/.cache/pypoetry/virtualenvs/sheetshuttle-PeNuXww9-py3.9/lib/python3.9/site-packages/pandas/core/internals/construction.py", line 883, in to_arrays
    content, columns = _finalize_columns_and_data(arr, columns, dtype)
  File "/home/noboshe/.cache/pypoetry/virtualenvs/sheetshuttle-PeNuXww9-py3.9/lib/python3.9/site-packages/pandas/core/internals/construction.py", line 985, in _finalize_columns_and_data
    raise ValueError(err) from err
ValueError: 2 columns passed, passed data had 5 columns