code: def get_common_parameters(input_files, collection=None):
      
      if collection is None:
          collection = "all"
      parameters = []
      for fn in input_files:
          fp = loadfile(fn, 'r')
          if collection == 'all':
              ps = fp[fp.samples_group].keys()
          else:
              ps = fp.attrs[collection]
          parameters.append(set(ps))
          fp.close()
      parameters = list(set.intersection(*parameters))
      if parameters == []:
          raise ValueError("no common parameters found for collection {} in "
                           "files {}".format(collection, ', '.join(input_files)))
      return parameters
docs: Gets a list of variable params that are common across all input files.
  
      If no common parameters are found, a ``ValueError`` is raised.
  
      Parameters
      ----------
      input_files : list of str
          List of input files to load.
      collection : str, optional
          What group of parameters to load. Can be the name of a list of
          parameters stored in the files' attrs (e.g., "variable_params"), or
          "all". If "all", will load all of the parameters in the files'
          samples group. Default is to load all.
  
      Returns
      -------
      list :
          List of the parameter names.