docs: def removeModifications(peptide):
      """Removes all modifications from a peptide string and return the plain
      amino acid sequence.
  
      :param peptide: peptide sequence, modifications have to be written in the
          format "[modificationName]"
      :param peptide: str
  
      :returns: amino acid sequence of ``peptide`` without any modifications
      """
      while peptide.find('[') != -1:
          peptide = peptide.split('[', 1)[0] + peptide.split(']', 1)[1]
      return peptide