def _merge_columns(self, columns):
merged_columns = list(columns)
has_merged_column = True
while has_merged_column:
has_merged_column = False
for i in range(0, len(merged_columns)):
c1 = merged_columns[i]
for j in range(i + 1, len(merged_columns)):
c2 = merged_columns[j]
if ColumnLayout.is_mergeable(c1, c2):
new_column = ColumnLayout.merge(c1, c2)
merged_columns.remove(c1)
merged_columns.remove(c2)
merged_columns.append(new_column)
has_merged_column = True
break
if has_merged_column:
break
return merged_columns
