code: def from_numpy3d_to_numpyflat(obj, store=None):
      if not isinstance(obj, np.ndarray) or len(obj.shape) != 3:
          raise TypeError("obj must be a 3D numpy.ndarray")
  
      shape = obj.shape
  
      # store second dimension shape/length if we want to restore
      if isinstance(store, dict):
          store["numpy_second_dim"] = shape[1]
  
      obj_in_2D = obj.reshape(shape[0], shape[1] * shape[2])
  
      return obj_in_2D
  
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 46 for calling a global function with example usage: from_numpy3d_to_numpyflat(obj, store) and returns: obj_in_2D