Safegraph is failing tests in main
Safegraph is failing tests in main; probably due to a collision of geo mapper changes:
```
ERROR test_run.py::TestRun::test_output_files_exist - KeyError: "['geo_id'] not in index"
ERROR test_run.py::TestRun::test_output_files_format - KeyError: "['geo_id'] not in index"
```


Traceback 1:
```
_____________________________________________________________________________________________ ERROR at setup of TestRun.test_output_files_exist ______________________________________________________________________________________________
multiprocessing.pool.RemoteTraceback:
"""
Traceback (most recent call last):
  File "/usr/lib/python3.8/multiprocessing/pool.py", line 125, in worker
    result = (True, func(*args, **kwds))
  File "/usr/lib/python3.8/multiprocessing/pool.py", line 48, in mapstar
    return list(map(*args))
  File "/home/krivard/projects/covid/dev/covidcast-indicators/safegraph/delphi_safegraph/process.py", line 236, in process
    process_window(past_week[:1],
  File "/home/krivard/projects/covid/dev/covidcast-indicators/safegraph/delphi_safegraph/process.py", line 183, in process_window
    df_export = aggregated_df[
  File "/home/krivard/projects/covid/dev/covidcast-indicators/safegraph/env/lib/python3.8/site-packages/pandas/core/frame.py", line 2912, in __getitem__
    indexer = self.loc._get_listlike_indexer(key, axis=1, raise_missing=True)[1]
  File "/home/krivard/projects/covid/dev/covidcast-indicators/safegraph/env/lib/python3.8/site-packages/pandas/core/indexing.py", line 1254, in _get_listlike_indexer
    self._validate_read_indexer(keyarr, indexer, axis, raise_missing=raise_missing)
  File "/home/krivard/projects/covid/dev/covidcast-indicators/safegraph/env/lib/python3.8/site-packages/pandas/core/indexing.py", line 1304, in _validate_read_indexer
    raise KeyError(f"{not_found} not in index")
KeyError: "['geo_id'] not in index"
"""

The above exception was the direct cause of the following exception:

    @pytest.fixture(scope="session")
    def run_as_module():
        # Clean receiving directory
        for fname in os.listdir("receiving"):
            if ".csv" in fname:
                os.remove(join("receiving", fname))
>       run_module()

conftest.py:17:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
../delphi_safegraph/run.py:76: in run_module
    pool.map(single_arg_process, files_with_previous_weeks)
/usr/lib/python3.8/multiprocessing/pool.py:364: in map
    return self._map_async(func, iterable, mapstar, chunksize).get()   
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <multiprocessing.pool.MapResult object at 0x7f927004e0a0>, timeout = None

    def get(self, timeout=None):
        self.wait(timeout)
        if not self.ready():
            raise TimeoutError
        if self._success:
            return self._value
        else:
>           raise self._value
E           KeyError: "['geo_id'] not in index"

/usr/lib/python3.8/multiprocessing/pool.py:771: KeyError
```

Traceback 2:
```
_____________________________________________________________________________________________ ERROR at setup of TestRun.test_output_files_format _____________________________________________________________________________________________
multiprocessing.pool.RemoteTraceback:
"""
Traceback (most recent call last):
  File "/usr/lib/python3.8/multiprocessing/pool.py", line 125, in worker
    result = (True, func(*args, **kwds))
  File "/usr/lib/python3.8/multiprocessing/pool.py", line 48, in mapstar
    return list(map(*args))
  File "/home/krivard/projects/covid/dev/covidcast-indicators/safegraph/delphi_safegraph/process.py", line 236, in process
    process_window(past_week[:1],
  File "/home/krivard/projects/covid/dev/covidcast-indicators/safegraph/delphi_safegraph/process.py", line 183, in process_window
    df_export = aggregated_df[
  File "/home/krivard/projects/covid/dev/covidcast-indicators/safegraph/env/lib/python3.8/site-packages/pandas/core/frame.py", line 2912, in __getitem__
    indexer = self.loc._get_listlike_indexer(key, axis=1, raise_missing=True)[1]
  File "/home/krivard/projects/covid/dev/covidcast-indicators/safegraph/env/lib/python3.8/site-packages/pandas/core/indexing.py", line 1254, in _get_listlike_indexer
    self._validate_read_indexer(keyarr, indexer, axis, raise_missing=raise_missing)
  File "/home/krivard/projects/covid/dev/covidcast-indicators/safegraph/env/lib/python3.8/site-packages/pandas/core/indexing.py", line 1304, in _validate_read_indexer
    raise KeyError(f"{not_found} not in index")
KeyError: "['geo_id'] not in index"
"""

The above exception was the direct cause of the following exception:

    @pytest.fixture(scope="session")
    def run_as_module():
        # Clean receiving directory
        for fname in os.listdir("receiving"):
            if ".csv" in fname:
                os.remove(join("receiving", fname))
>       run_module()

conftest.py:17:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
../delphi_safegraph/run.py:76: in run_module
    pool.map(single_arg_process, files_with_previous_weeks)
/usr/lib/python3.8/multiprocessing/pool.py:364: in map
    return self._map_async(func, iterable, mapstar, chunksize).get()   
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <multiprocessing.pool.MapResult object at 0x7f927004e0a0>, timeout = None

    def get(self, timeout=None):
        self.wait(timeout)
        if not self.ready():
            raise TimeoutError
        if self._success:
            return self._value
        else:
>           raise self._value
E           KeyError: "['geo_id'] not in index"

/usr/lib/python3.8/multiprocessing/pool.py:771: KeyError
```

diff --git a/safegraph/delphi_safegraph/process.py b/safegraph/delphi_safegraph/process.py
index adb0a208..e7c3846e 100644
--- a/safegraph/delphi_safegraph/process.py
+++ b/safegraph/delphi_safegraph/process.py
@@ -122,10 +122,11 @@ def aggregate(df, signal_names, geo_resolution='county'):
     """
     # Prepare geo resolution
     if geo_resolution == 'county':
-        df['geo_id'] = df['county_fips']
+        geo_transformed_df = df.copy()
+        geo_transformed_df['geo_id'] = df['county_fips']
     elif geo_resolution == 'state':
         gmpr = GeoMapper()
-        df = gmpr.add_geocode(df,
+        geo_transformed_df = gmpr.add_geocode(df,
                               from_col='county_fips',
                               from_code='fips',
                               new_code='state_id',
@@ -136,7 +137,7 @@ def aggregate(df, signal_names, geo_resolution='county'):
             f'`geo_resolution` must be one of {GEO_RESOLUTIONS}.')
 
     # Aggregation and signal creation
-    grouped_df = df.groupby(['geo_id'])[signal_names]
+    grouped_df = geo_transformed_df.groupby(['geo_id'])[signal_names]
     df_mean = grouped_df.mean()
     df_sd = grouped_df.std()
     df_n = grouped_df.count()
['safegraph/delphi_safegraph/process.py']