Consider this MWE:

import pyparsing

code = '"""this is a\nmulti-line  # not an actual comment\nstring"""'

comment_filter = pyparsing.python_style_comment.suppress()
print(comment_filter.transform_string(code))

where code is a valid Python program that contains only a single multi-line string:

"""this is a
multi-line  # not an actual comment
string"""

This string contains a # character, but since it is within the string, it should not be treated as a comment. pyparsing does so, however. Output of the above MWE:

"""this is a
multi-line
string"""

where # not an actual comment has been incorrectly removed.