code: def is_equal_to_ignoring_case(self, other):
          
          if not isinstance(self.val, str_types):
              raise TypeError('val is not a string')
          if not isinstance(other, str_types):
              raise TypeError('given arg must be a string')
          if self.val.lower() != other.lower():
              self._err('Expected <%s> to be case-insensitive equal to <%s>, but was not.' % (self.val, other))
          return self
docs: Asserts that val is case-insensitive equal to other.