parameters: (self, level_index: Index, key: Hashable)
docstring: If key is NA value, location of index unify as -1.
  
          Parameters
          ----------
          level_index: Index
          key : label
  
          Returns
          -------
          loc : int
              If key is NA value, loc is -1
              Else, location of key in index.
  
          See Also
          --------
          Index.get_loc : The get_loc method for (single-level) index.
docstring_summary: If key is NA value, location of index unify as -1.
docstring_tokens: If key is NA value location of index unify as - 1 .
function: def _get_loc_single_level_index(self, level_index: Index, key: Hashable) -> int:
          """
          If key is NA value, location of index unify as -1.
  
          Parameters
          ----------
          level_index: Index
          key : label
  
          Returns
          -------
          loc : int
              If key is NA value, loc is -1
              Else, location of key in index.
  
          See Also
          --------
          Index.get_loc : The get_loc method for (single-level) index.
          """
  
          if is_scalar(key) and isna(key):
              return -1
          else:
              return level_index.get_loc(key)
function_tokens: def _get_loc_single_level_index ( self , level_index : Index , key : Hashable ) -> int : if is_scalar ( key ) and isna ( key ) : return - 1 else : return level_index . get_loc ( key )