code: def get_okeeffe_params(el_symbol):
      
  
      el = Element(el_symbol)
      if el not in list(BV_PARAMS.keys()):
          raise RuntimeError("Could not find O'Keeffe parameters for element"
                             " \"{}\" in \"BV_PARAMS\"dictonary"
                             " provided by pymatgen".format(el_symbol))
  
      return BV_PARAMS[el]
docs: Returns the elemental parameters related to atom size and
      electronegativity which are used for estimating bond-valence
      parameters (bond length) of pairs of atoms on the basis of data
      provided in 'Atoms Sizes and Bond Lengths in Molecules and Crystals'
      (O'Keeffe & Brese, 1991).
  
      Args:
          el_symbol (str): element symbol.
      Returns:
          (dict): atom-size ('r') and electronegativity-related ('c')
                  parameter.