text: # -*- coding: utf-8 -*-
  """Module for radii lookups"""
  import warnings
  
  import numpy as np
  
  from .definitions import COVALENT_RADII, VDW_RADII
  
  _COVALENT_RADII_MEDIAN = np.median(list(COVALENT_RADII.values()))
  _VDW_RADII_MEDIAN = np.median(list(VDW_RADII.values()))
  
  
  def _get_covalent_radius(element):
      try:
          radius = COVALENT_RADII[element]
  
      except KeyError:
          radius = _COVALENT_RADII_MEDIAN
          warnings.warn(
              f"Covalent radius for {element} unknown. Using median {radius:.2f}."
          )
      return radius
  
  
  def _get_vdw_radius(element):
      try:
          radius = VDW_RADII[element]
  
      except KeyError:
          radius = _VDW_RADII_MEDIAN
          warnings.warn(
              f"Van-der-Waals radius for {element} unknown. Using median {radius:.2f}."
          )
      return radius
  