text: ''' Utilities for checking dependencies
  
  '''
  from importlib import import_module
  
  def import_optional(mod_name):
      ''' Attempt to import an optional dependency.
  
      Silently returns None if the requested module is not available.
  
      Args:
          mod_name (str) : name of the optional module to try to import
  
      Returns:
          imported module or None, if import fails
  
      '''
      try:
          return import_module(mod_name)
      except ImportError:
          return None
  
  def import_required(mod_name, error_msg):
      ''' Attempt to import a required dependency.
  
      Raises a RuntimeError if the requested module is not available.
  
      Args:
          mod_name (str) : name of the required module to try to import
          error_msg (str) : error message to raise when the module is missing
  
      Returns:
          imported module
  
      Raises:
          RuntimeError
  
      '''
      try:
          return import_module(mod_name)
      except ImportError:
          raise RuntimeError(error_msg)
  