docs: def load_ini(filename):
      """
      Read a CLASS ``.ini`` file, returning a dictionary of parameters
  
      Parameters
      ----------
      filename : str
          the name of an existing parameter file to load, or one included as
          part of the CLASS source
  
      Returns
      -------
      dict :
          the input parameters loaded from file
      """
      # also look in data dir
      path = _find_file(filename)
  
      pars = {}
      with open(path, 'r') as ff:
  
          # loop over lines
          for lineno, line in enumerate(ff):
              if not line: continue
  
              # skip any commented lines with #
              if '#' in line: line = line[line.index('#')+1:]
  
              # must have an equals sign to be valid
              if "=" not in line: continue
  
              # extract key and value pairs
              fields = line.split("=")
              if len(fields) != 2:
                  import warnings
                  warnings.warn("skipping line number %d: '%s'" %(lineno,line))
                  continue
              pars[fields[0].strip()] = fields[1].strip()
  
      return pars