Fix a spelling error in a Python documentation string

Author: amn

expand-macros.py

@@ -2,7 +2,7 @@
 
 Macro processing refers here to eager rewriting/replacement/substitution of Python code constructs decorated with the "syntactic" (no definition available normally, when the containing module is imported) decorator `macro`. The purpose of such processing is to implement the equivalent to what is usually called "pre-processing" for e.g. C/C++ language(s). As `macro`-decorated procedures (only decorating of procedures is currently effectively supported for `macro`) are encountered during processing of Python code, the entire procedure is removed and "unparsed" equivalent of the series of AST statements it returned, are inserted in its place instead.
 
-This implements powerful and "semantically-aware" code pre-processing mechanism, for situations demanding it. Our immediate need with this was to allow type checkers like MyPy to be able to analyze as much of the project's Python code as possible, which these are normally unable to do in cases of so-called dynamically created types (and consequently object(s) of such types). And so instead of living with effectively uncheckable dynamic types created with the `type` built-in -- for e.g. `Token` subclasses -- we employ _pre-processing_ of Python code into Python code which lends to type-checking, a benefit we deemed to ba a "must-have" for the project.
+This implements powerful and "semantically-aware" code pre-processing mechanism, for situations demanding it. Our immediate need with this was to allow type checkers like MyPy to be able to analyze as much of the project's Python code as possible, which these are normally unable to do in cases of so-called dynamically created types (and consequently object(s) of such types). And so instead of living with effectively uncheckable dynamic types created with the `type` built-in -- for e.g. `Token` subclasses -- we employ _pre-processing_ of Python code into Python code which lends to type-checking, a benefit we deemed to be a "must-have" for the project.
 """
 
 import ast