ENH: Remove restriction on writing newlines in header

Author: effigies

nibabel/streamlines/tck.py

@@ -266,11 +266,6 @@ def _write_header(fileobj, header):
         )
         out = '\n'.join(lines)
 
-        # Check the header is well formatted.
-        if out.count('\n') > len(lines) - 1:  # \n only allowed between lines.
-            msg = f"Key-value pairs cannot contain '\\n':\n{out}"
-            raise HeaderError(msg)
-
         if out.count(':') > len(lines):
             # : only one per line (except the last one which contains END).
             msg = f"Key-value pairs cannot contain ':':\n{out}"

nibabel/streamlines/tests/test_tck.py

@@ -192,10 +192,6 @@ def test_write_simple_file(self):
         # TCK file containing not well formatted entries in its header.
         tck_file = BytesIO()
         tck = TckFile(tractogram)
-        tck.header['new_entry'] = 'value\n'  # \n not allowed
-        with pytest.raises(HeaderError):
-            tck.save(tck_file)
-
         tck.header['new_entry'] = 'val:ue'  # : not allowed
         with pytest.raises(HeaderError):
             tck.save(tck_file)