Populates the Table with a list of tuples of strings.

        Args:
            matrix (list): list of iterables of strings (lists or something else). 
                Items in the matrix have to correspond to a key for the children.

def define_grid(self, matrix):
        """Populates the Table with a list of tuples of strings.

        Args:
            matrix (list): list of iterables of strings (lists or something else). 
                Items in the matrix have to correspond to a key for the children.
        """
        self.style['grid-template-areas'] = ''.join("'%s'"%(' '.join(x)) for x in matrix)