added closestMatch suggestion

src/dsiParser.py

 from dataclasses import dataclass
 import re
 import warnings
+import difflib
 
 class dsiParser:
     """Parser to parse D-SI unit string into a tree
@@ -256,7 +257,31 @@ def _warn(message: str, warningClass):
     """
     warnings.warn(message, warningClass)
     return message
-            
+
+def _getClosestStrAndType(unkownStr):
+    """returns the closest string and type of the given string
+
+    Args:
+        unkownStr (str): string to be compared
+
+    Returns:
+        str: closest string
+        str: type of closest string
+    """
+    closestStr = difflib.get_close_matches(unkownStr, _dsiPrefixesLatex.keys(), n=1)
+    if len(closestStr) == 0:
+        closestStr = difflib.get_close_matches(unkownStr, _dsiUnitsLatex.keys(), n=1)
+        if len(closestStr) == 0:
+            closestStr = difflib.get_close_matches(unkownStr, _dsiKeyWords.keys(), n=1)
+            if len(closestStr) == 0:
+                return (unkownStr, 'unknown')
+            else:
+                return (closestStr[0], 'keyWord')
+        else:
+            return (closestStr[0], 'unit')
+    else:
+        return (closestStr[0], 'prefix')
+
 # mapping D-SI prefixes to latex
 _dsiPrefixesLatex = {
     'deca': r'\mathrm{da}',
@@ -330,4 +355,7 @@ _dsiUnitsLatex = {
     'bel': r'\mathrm{B}',
     'decibel': r'\mathrm{dB}'
 }
-    
+
\ No newline at end of file
+_dsiKeyWords = {
+    'tothe': r'\tothe',
+    'per': r'\per'}
\ No newline at end of file

tests/test_main.py

 import pytest
-from dsiParser import dsiParser, _node
+from dsiParser import dsiParser, _node, _getClosestStrAndType
 
 p = dsiParser()
 
@@ -100,3 +100,11 @@ def test_wrappers():
     assert parserWrapper.parse(r'\metre').toLatex() == r'&\mathrm{m}&'
     parserFull = dsiParser(latexDefaultWrapper='@', latexDefaultPrefix=r'\mathrm{Prefix}', latexDefaultSuffix=r'\mathrm{Suffix}')
     assert parserFull.parse(r'\metre').toLatex() == r'@\mathrm{Prefix}\mathrm{m}\mathrm{Suffix}@'
+
+def test_getClosestMatch():
+    closestMatch = _getClosestStrAndType('\kiilo')
+    assert closestMatch == ('kilo','prefix')
+    closestMatch = _getClosestStrAndType('\mettre')
+    assert closestMatch == ('metre','unit')
+    closestMatch = _getClosestStrAndType(r'\ttothe')
+    assert closestMatch == ('tothe', 'keyWord')