prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  multiplication doesn't seem to work in d.transform
  `d.transform('w2+w2+w2', 'w1', 'd2')` works.
  
  `d.transform('3*w2', 'w1', 'd2')` does not work (even with varying spacing around the multiplication operator)
  Part of the error that is raised:
  ```
    File "/home/darien/source/WrightTools/WrightTools/data/_data.py", line 1306, in transform
      axis = current.get(expression, Axis(self, expression))
  
    File "/home/darien/source/WrightTools/WrightTools/data/_axis.py", line 53, in __init__
      self.units = self.variables[0].units
  
    File "/home/darien/source/WrightTools/WrightTools/data/_axis.py", line 152, in variables
      return self._variables
  
  AttributeError: 'Axis' object has no attribute '_variables'
  ```
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `WrightTools/data/_axis.py`
  Content:
  ```
  1 """Axis class and associated."""
  2 
  3 
  4 # --- import --------------------------------------------------------------------------------------
  5 
  6 
  7 import re
  8 import numexpr
  9 import operator
  10 import functools
  11 
  12 import numpy as np
  13 
  14 from .. import exceptions as wt_exceptions
  15 from .. import kit as wt_kit
  16 from .. import units as wt_units
  17 
  18 
  19 # --- define --------------------------------------------------------------------------------------
  20 
  21 
  22 operator_to_identifier = {}
  23 operator_to_identifier['/'] = '__d__'
  24 operator_to_identifier['='] = '__e__'
  25 operator_to_identifier['-'] = '__m__'
  26 operator_to_identifier['+'] = '__p__'
  27 operator_to_identifier['*'] = '__t__'
  28 identifier_to_operator = {value: key for key, value in operator_to_identifier.items()}
  29 operators = ''.join(operator_to_identifier.keys())
  30 
  31 
  32 # --- class ---------------------------------------------------------------------------------------
  33 
  34 
  35 class Axis(object):
  36     """Axis class."""
  37 
  38     def __init__(self, parent, expression, units=None):
  39         """Data axis.
  40 
  41         Parameters
  42         ----------
  43         parent : WrightTools.Data
  44             Parent data object.
  45         expression : string
  46             Axis expression.
  47         units : string (optional)
  48             Axis units. Default is None.
  49         """
  50         self.parent = parent
  51         self.expression = expression
  52         if units is None:
  53             self.units = self.variables[0].units
  54         else:
  55             self.units = units
  56 
  57     def __getitem__(self, index):
  58         vs = {}
  59         for variable in self.variables:
  60             arr = variable[index]
  61             vs[variable.natural_name] = wt_units.converter(arr, variable.units, self.units)
  62         return numexpr.evaluate(self.expression.split('=')[0], local_dict=vs)
  63 
  64     def __repr__(self):
  65         return '<WrightTools.Axis {0} ({1}) at {2}>'.format(self.expression, str(self.units),
  66                                                             id(self))
  67 
  68     @property
  69     def _leaf(self):
  70         out = self.expression
  71         if self.units is not None:
  72             out += ' ({0}) {1}'.format(self.units, self.shape)
  73         return out
  74 
  75     @property
  76     def full(self):
  77         arr = self[:]
  78         for i in range(arr.ndim):
  79             if arr.shape[i] == 1:
  80                 arr = np.repeat(arr, self.parent.shape[i], axis=i)
  81         return arr
  82 
  83     @property
  84     def identity(self):
  85         return self.natural_name + ' {%s}' % self.units
  86 
  87     @property
  88     def label(self):
  89         symbol = wt_units.get_symbol(self.units)
  90         label = r'$\mathsf{' + self.expression
  91         for v in self.variables:
  92             label = label.replace(v.natural_name, '%s_{%s}' % (symbol, v.label))
  93         if self.units_kind:
  94             units_dictionary = getattr(wt_units, self.units_kind)
  95             label += r'\,'
  96             label += r'\left('
  97             label += units_dictionary[self.units][2]
  98             label += r'\right)'
  99         else:
  100             pass
  101         label += r'}$'
  102         return label
  103 
  104     @property
  105     def natural_name(self):
  106         name = self.expression.strip()
  107         for op in operators:
  108             name = name.replace(op, operator_to_identifier[op])
  109         return name
  110 
  111     @property
  112     def ndim(self):
  113         """Get number of dimensions."""
  114         try:
  115             assert self._ndim is not None
  116         except (AssertionError, AttributeError):
  117             self._ndim = self.variables[0].ndim
  118         finally:
  119             return self._ndim
  120 
  121     @property
  122     def points(self):
  123         """Squeezed array."""
  124         return np.squeeze(self[:])
  125 
  126     @property
  127     def shape(self):
  128         """Shape."""
  129         return wt_kit.joint_shape(*self.variables)
  130 
  131     @property
  132     def size(self):
  133         """Size."""
  134         return functools.reduce(operator.mul, self.shape)
  135 
  136     @property
  137     def units_kind(self):
  138         """Units kind."""
  139         return wt_units.kind(self.units)
  140 
  141     @property
  142     def variables(self):
  143         """Variables."""
  144         try:
  145             assert self._variables is not None
  146         except (AssertionError, AttributeError):
  147             pattern = '|'.join(map(re.escape, operators))
  148             keys = re.split(pattern, self.expression)
  149             indices = [self.parent.variable_names.index(key) for key in keys]
  150             self._variables = [self.parent.variables[i] for i in indices]
  151         finally:
  152             return self._variables
  153 
  154     def convert(self, destination_units, *, convert_variables=False):
  155         """Convert axis to destination_units.
  156 
  157         Parameters
  158         ----------
  159         destination_units : string
  160             Destination units.
  161         convert_variables : boolean (optional)
  162             Toggle conversion of stored arrays. Default is False.
  163         """
  164         if not wt_units.is_valid_conversion(self.units, destination_units):
  165             kind = wt_units.kind(self.units)
  166             valid = list(wt_units.dicts[kind].keys())
  167             raise wt_exceptions.UnitsError(valid, destination_units)
  168         if convert_variables:
  169             for v in self.variables:
  170                 v.convert(destination_units)
  171         self.units = destination_units
  172 
  173     def max(self):
  174         """Axis max."""
  175         return np.max(self[:])
  176 
  177     def min(self):
  178         """Axis min."""
  179         return np.min(self[:])
  180
  ```
  --- END FILES ---
  
  Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.
  
  Here is an example:
  
  ```diff
  diff --git a/examples/server_async.py b/examples/server_async.py
  --- a/examples/server_async.py
  +++ b/examples/server_async.py
  @@ -313,4 +313,4 @@
   
   
   if __name__ == "__main__":
  -    asyncio.run(run_async_server("."), debug=True)
  +    asyncio.run(run_async_server(), debug=True)
  diff --git a/examples/server_sync.py b/examples/server_sync.py
  --- a/examples/server_sync.py
  +++ b/examples/server_sync.py
  @@ -313,5 +313,5 @@
   
   
   if __name__ == "__main__":
  -    server = run_sync_server(".")
  +    server = run_sync_server()
       server.shutdown()
  
  ```
  
golden_diff: diff --git a/WrightTools/data/_axis.py b/WrightTools/data/_axis.py
  --- a/WrightTools/data/_axis.py
  +++ b/WrightTools/data/_axis.py
  @@ -106,7 +106,7 @@
           name = self.expression.strip()
           for op in operators:
               name = name.replace(op, operator_to_identifier[op])
  -        return name
  +        return wt_kit.string2identifier(name)
   
       @property
       def ndim(self):
  @@ -146,7 +146,10 @@
           except (AssertionError, AttributeError):
               pattern = '|'.join(map(re.escape, operators))
               keys = re.split(pattern, self.expression)
  -            indices = [self.parent.variable_names.index(key) for key in keys]
  +            indices = []
  +            for key in keys:
  +                if key in self.parent.variable_names:
  +                    indices.append(self.parent.variable_names.index(key))
               self._variables = [self.parent.variables[i] for i in indices]
           finally:
               return self._variables
  
verification_info: {"golden_diff": "diff --git a/WrightTools/data/_axis.py b/WrightTools/data/_axis.py\n--- a/WrightTools/data/_axis.py\n+++ b/WrightTools/data/_axis.py\n@@ -106,7 +106,7 @@\n         name = self.expression.strip()\n         for op in operators:\n             name = name.replace(op, operator_to_identifier[op])\n-        return name\n+        return wt_kit.string2identifier(name)\n \n     @property\n     def ndim(self):\n@@ -146,7 +146,10 @@\n         except (AssertionError, AttributeError):\n             pattern = '|'.join(map(re.escape, operators))\n             keys = re.split(pattern, self.expression)\n-            indices = [self.parent.variable_names.index(key) for key in keys]\n+            indices = []\n+            for key in keys:\n+                if key in self.parent.variable_names:\n+                    indices.append(self.parent.variable_names.index(key))\n             self._variables = [self.parent.variables[i] for i in indices]\n         finally:\n             return self._variables\n", "issue": "multiplication doesn't seem to work in d.transform\n`d.transform('w2+w2+w2', 'w1', 'd2')` works.\r\n\r\n`d.transform('3*w2', 'w1', 'd2')` does not work (even with varying spacing around the multiplication operator)\r\nPart of the error that is raised:\r\n```\r\n  File \"/home/darien/source/WrightTools/WrightTools/data/_data.py\", line 1306, in transform\r\n    axis = current.get(expression, Axis(self, expression))\r\n\r\n  File \"/home/darien/source/WrightTools/WrightTools/data/_axis.py\", line 53, in __init__\r\n    self.units = self.variables[0].units\r\n\r\n  File \"/home/darien/source/WrightTools/WrightTools/data/_axis.py\", line 152, in variables\r\n    return self._variables\r\n\r\nAttributeError: 'Axis' object has no attribute '_variables'\r\n```\n", "before_files": [{"content": "\"\"\"Axis class and associated.\"\"\"\n\n\n# --- import --------------------------------------------------------------------------------------\n\n\nimport re\nimport numexpr\nimport operator\nimport functools\n\nimport numpy as np\n\nfrom .. import exceptions as wt_exceptions\nfrom .. import kit as wt_kit\nfrom .. import units as wt_units\n\n\n# --- define --------------------------------------------------------------------------------------\n\n\noperator_to_identifier = {}\noperator_to_identifier['/'] = '__d__'\noperator_to_identifier['='] = '__e__'\noperator_to_identifier['-'] = '__m__'\noperator_to_identifier['+'] = '__p__'\noperator_to_identifier['*'] = '__t__'\nidentifier_to_operator = {value: key for key, value in operator_to_identifier.items()}\noperators = ''.join(operator_to_identifier.keys())\n\n\n# --- class ---------------------------------------------------------------------------------------\n\n\nclass Axis(object):\n    \"\"\"Axis class.\"\"\"\n\n    def __init__(self, parent, expression, units=None):\n        \"\"\"Data axis.\n\n        Parameters\n        ----------\n        parent : WrightTools.Data\n            Parent data object.\n        expression : string\n            Axis expression.\n        units : string (optional)\n            Axis units. Default is None.\n        \"\"\"\n        self.parent = parent\n        self.expression = expression\n        if units is None:\n            self.units = self.variables[0].units\n        else:\n            self.units = units\n\n    def __getitem__(self, index):\n        vs = {}\n        for variable in self.variables:\n            arr = variable[index]\n            vs[variable.natural_name] = wt_units.converter(arr, variable.units, self.units)\n        return numexpr.evaluate(self.expression.split('=')[0], local_dict=vs)\n\n    def __repr__(self):\n        return '<WrightTools.Axis {0} ({1}) at {2}>'.format(self.expression, str(self.units),\n                                                            id(self))\n\n    @property\n    def _leaf(self):\n        out = self.expression\n        if self.units is not None:\n            out += ' ({0}) {1}'.format(self.units, self.shape)\n        return out\n\n    @property\n    def full(self):\n        arr = self[:]\n        for i in range(arr.ndim):\n            if arr.shape[i] == 1:\n                arr = np.repeat(arr, self.parent.shape[i], axis=i)\n        return arr\n\n    @property\n    def identity(self):\n        return self.natural_name + ' {%s}' % self.units\n\n    @property\n    def label(self):\n        symbol = wt_units.get_symbol(self.units)\n        label = r'$\\mathsf{' + self.expression\n        for v in self.variables:\n            label = label.replace(v.natural_name, '%s_{%s}' % (symbol, v.label))\n        if self.units_kind:\n            units_dictionary = getattr(wt_units, self.units_kind)\n            label += r'\\,'\n            label += r'\\left('\n            label += units_dictionary[self.units][2]\n            label += r'\\right)'\n        else:\n            pass\n        label += r'}$'\n        return label\n\n    @property\n    def natural_name(self):\n        name = self.expression.strip()\n        for op in operators:\n            name = name.replace(op, operator_to_identifier[op])\n        return name\n\n    @property\n    def ndim(self):\n        \"\"\"Get number of dimensions.\"\"\"\n        try:\n            assert self._ndim is not None\n        except (AssertionError, AttributeError):\n            self._ndim = self.variables[0].ndim\n        finally:\n            return self._ndim\n\n    @property\n    def points(self):\n        \"\"\"Squeezed array.\"\"\"\n        return np.squeeze(self[:])\n\n    @property\n    def shape(self):\n        \"\"\"Shape.\"\"\"\n        return wt_kit.joint_shape(*self.variables)\n\n    @property\n    def size(self):\n        \"\"\"Size.\"\"\"\n        return functools.reduce(operator.mul, self.shape)\n\n    @property\n    def units_kind(self):\n        \"\"\"Units kind.\"\"\"\n        return wt_units.kind(self.units)\n\n    @property\n    def variables(self):\n        \"\"\"Variables.\"\"\"\n        try:\n            assert self._variables is not None\n        except (AssertionError, AttributeError):\n            pattern = '|'.join(map(re.escape, operators))\n            keys = re.split(pattern, self.expression)\n            indices = [self.parent.variable_names.index(key) for key in keys]\n            self._variables = [self.parent.variables[i] for i in indices]\n        finally:\n            return self._variables\n\n    def convert(self, destination_units, *, convert_variables=False):\n        \"\"\"Convert axis to destination_units.\n\n        Parameters\n        ----------\n        destination_units : string\n            Destination units.\n        convert_variables : boolean (optional)\n            Toggle conversion of stored arrays. Default is False.\n        \"\"\"\n        if not wt_units.is_valid_conversion(self.units, destination_units):\n            kind = wt_units.kind(self.units)\n            valid = list(wt_units.dicts[kind].keys())\n            raise wt_exceptions.UnitsError(valid, destination_units)\n        if convert_variables:\n            for v in self.variables:\n                v.convert(destination_units)\n        self.units = destination_units\n\n    def max(self):\n        \"\"\"Axis max.\"\"\"\n        return np.max(self[:])\n\n    def min(self):\n        \"\"\"Axis min.\"\"\"\n        return np.min(self[:])\n", "path": "WrightTools/data/_axis.py"}], "after_files": [{"content": "\"\"\"Axis class and associated.\"\"\"\n\n\n# --- import --------------------------------------------------------------------------------------\n\n\nimport re\nimport numexpr\nimport operator\nimport functools\n\nimport numpy as np\n\nfrom .. import exceptions as wt_exceptions\nfrom .. import kit as wt_kit\nfrom .. import units as wt_units\n\n\n# --- define --------------------------------------------------------------------------------------\n\n\noperator_to_identifier = {}\noperator_to_identifier['/'] = '__d__'\noperator_to_identifier['='] = '__e__'\noperator_to_identifier['-'] = '__m__'\noperator_to_identifier['+'] = '__p__'\noperator_to_identifier['*'] = '__t__'\nidentifier_to_operator = {value: key for key, value in operator_to_identifier.items()}\noperators = ''.join(operator_to_identifier.keys())\n\n\n# --- class ---------------------------------------------------------------------------------------\n\n\nclass Axis(object):\n    \"\"\"Axis class.\"\"\"\n\n    def __init__(self, parent, expression, units=None):\n        \"\"\"Data axis.\n\n        Parameters\n        ----------\n        parent : WrightTools.Data\n            Parent data object.\n        expression : string\n            Axis expression.\n        units : string (optional)\n            Axis units. Default is None.\n        \"\"\"\n        self.parent = parent\n        self.expression = expression\n        if units is None:\n            self.units = self.variables[0].units\n        else:\n            self.units = units\n\n    def __getitem__(self, index):\n        vs = {}\n        for variable in self.variables:\n            arr = variable[index]\n            vs[variable.natural_name] = wt_units.converter(arr, variable.units, self.units)\n        return numexpr.evaluate(self.expression.split('=')[0], local_dict=vs)\n\n    def __repr__(self):\n        return '<WrightTools.Axis {0} ({1}) at {2}>'.format(self.expression, str(self.units),\n                                                            id(self))\n\n    @property\n    def _leaf(self):\n        out = self.expression\n        if self.units is not None:\n            out += ' ({0}) {1}'.format(self.units, self.shape)\n        return out\n\n    @property\n    def full(self):\n        arr = self[:]\n        for i in range(arr.ndim):\n            if arr.shape[i] == 1:\n                arr = np.repeat(arr, self.parent.shape[i], axis=i)\n        return arr\n\n    @property\n    def identity(self):\n        return self.natural_name + ' {%s}' % self.units\n\n    @property\n    def label(self):\n        symbol = wt_units.get_symbol(self.units)\n        label = r'$\\mathsf{' + self.expression\n        for v in self.variables:\n            label = label.replace(v.natural_name, '%s_{%s}' % (symbol, v.label))\n        if self.units_kind:\n            units_dictionary = getattr(wt_units, self.units_kind)\n            label += r'\\,'\n            label += r'\\left('\n            label += units_dictionary[self.units][2]\n            label += r'\\right)'\n        else:\n            pass\n        label += r'}$'\n        return label\n\n    @property\n    def natural_name(self):\n        name = self.expression.strip()\n        for op in operators:\n            name = name.replace(op, operator_to_identifier[op])\n        return wt_kit.string2identifier(name)\n\n    @property\n    def ndim(self):\n        \"\"\"Get number of dimensions.\"\"\"\n        try:\n            assert self._ndim is not None\n        except (AssertionError, AttributeError):\n            self._ndim = self.variables[0].ndim\n        finally:\n            return self._ndim\n\n    @property\n    def points(self):\n        \"\"\"Squeezed array.\"\"\"\n        return np.squeeze(self[:])\n\n    @property\n    def shape(self):\n        \"\"\"Shape.\"\"\"\n        return wt_kit.joint_shape(*self.variables)\n\n    @property\n    def size(self):\n        \"\"\"Size.\"\"\"\n        return functools.reduce(operator.mul, self.shape)\n\n    @property\n    def units_kind(self):\n        \"\"\"Units kind.\"\"\"\n        return wt_units.kind(self.units)\n\n    @property\n    def variables(self):\n        \"\"\"Variables.\"\"\"\n        try:\n            assert self._variables is not None\n        except (AssertionError, AttributeError):\n            pattern = '|'.join(map(re.escape, operators))\n            keys = re.split(pattern, self.expression)\n            indices = []\n            for key in keys:\n                if key in self.parent.variable_names:\n                    indices.append(self.parent.variable_names.index(key))\n            self._variables = [self.parent.variables[i] for i in indices]\n        finally:\n            return self._variables\n\n    def convert(self, destination_units, *, convert_variables=False):\n        \"\"\"Convert axis to destination_units.\n\n        Parameters\n        ----------\n        destination_units : string\n            Destination units.\n        convert_variables : boolean (optional)\n            Toggle conversion of stored arrays. Default is False.\n        \"\"\"\n        if not wt_units.is_valid_conversion(self.units, destination_units):\n            kind = wt_units.kind(self.units)\n            valid = list(wt_units.dicts[kind].keys())\n            raise wt_exceptions.UnitsError(valid, destination_units)\n        if convert_variables:\n            for v in self.variables:\n                v.convert(destination_units)\n        self.units = destination_units\n\n    def max(self):\n        \"\"\"Axis max.\"\"\"\n        return np.max(self[:])\n\n    def min(self):\n        \"\"\"Axis min.\"\"\"\n        return np.min(self[:])\n", "path": "WrightTools/data/_axis.py"}]}