code: def from_multiindex_to_long(obj, store=None):
      X_long = pd.melt(obj, value_vars=obj.columns, ignore_index=False)
      X_long = X_long.reset_index()
  
      return X_long
  
imports: import numpy
  import pandas
  from sktime.datatypes._convert_utils._coerce import _coerce_df_dtypes
  from sktime.datatypes._convert_utils._convert import _extend_conversions
  from sktime.datatypes._panel._registry import MTYPE_LIST_PANEL
  from sktime.utils.pandas import df_map
  from sktime.utils.validation._dependencies import _check_soft_dependencies
label_desc: Use image node_id 25 for calling a global function with example usage: from_multiindex_to_long(obj, store) and returns: X_long