docs: def load_mutation_rates(path=None):
      """ load sequence context-based mutation rates
      
      Args:
          path: path to table of sequence context-based mutation rates. If None,
              this defaults to per-trinucleotide rates provided by Kaitlin Samocha
              (Broad Institute).
      
      Returns:
          list of [initial, changed, rate] lists e.g. [['AGA', 'ATA', '5e-8']]
      """
      
      if path is None:
          path = resource_filename(__name__, "data/rates.txt")
      
      rates = []
      with open(path) as handle:
          for line in handle:
              if line.startswith("from"): # ignore the header line
                  continue
              
              line = [ x.encode('utf8') for x in line.strip().split() ]
              rates.append(line)
      
      return rates