docs: def set_patch(self, pre_release_tag=''):
          """
          Increment the patch number of project
  
          :var release_tag describes the tag ('a', 'b', 'rc', ...)
          :var release_tag_version describes the number behind the 'a', 'b' or 'rc'
          For e.g.:
          """
  
          current_version = self.get_version()
          current_patch = self.get_patch_version(current_version)
          current_pre_release_tag = self.get_current_pre_release_tag(current_patch)
          current_RELEASE_SEPARATOR = self.get_current_RELEASE_SEPARATOR(current_patch)
          new_patch = ''
  
          # The new patch should get a release tag
          if pre_release_tag:
  
              # Check, if the current patch already contains a pre_release_tag.
              if current_pre_release_tag:
                  new_patch = str(current_patch.split(current_pre_release_tag, 2)[0]) + pre_release_tag
  
                  if pre_release_tag == current_pre_release_tag:
                      new_patch += str(int(current_patch.split(current_pre_release_tag, 2)[1])+1)
                  else:
                      new_patch += '0'
  
              # The current patch does not contains a pre_release_tag.
              else:
                  new_patch = str(int(current_patch)+1) + \
                              APISettings.RELEASE_SEPARATOR + \
                              pre_release_tag + \
                              '0'
  
          # The new patch should not contain any tag. So just increase it.
          else:
              if current_RELEASE_SEPARATOR:
                  new_patch = str(int(current_patch.split(current_RELEASE_SEPARATOR, 2)[0])+1)
              elif current_pre_release_tag:
                  new_patch = str(int(current_patch.split(current_pre_release_tag, 2)[0])+1)
              else:
                  new_patch = str(int(current_patch)+1)
  
          new_version = str(int(current_version.split('.', 5)[0])) + '.' + \
              str(int(current_version.split('.', 5)[1])) + '.' + \
              str(new_patch)
          self.set_version(current_version, new_version)