prompt: You will be provided with a partial code base and an issue statement explaining a problem to resolve.
  <issue>
  Add nullable attribute to the Team Model
  Following changes are required in the Team model: 
  
  - [x] Convert the URLFields to CharField with URL
  
  - [x] Change the fields `email`, `github_url`, `linkedin_url`, `personal_website` to nullable fields
  
  </issue>
  <code>
  [start of apps/web/models.py]
  1 from __future__ import unicode_literals
  2 
  3 from django.db import models
  4 
  5 from base.models import (TimeStampedModel, )
  6 
  7 
  8 class Contact(TimeStampedModel):
  9     """Model representing details of User submitting queries."""
  10     name = models.CharField(max_length=100,)
  11     email = models.EmailField(max_length=70,)
  12     message = models.CharField(max_length=500,)
  13 
  14     def __unicode__(self):
  15         return "%s: %s: %s" % (self.name, self.email, self.message)
  16 
  17     class Meta:
  18         app_label = 'web'
  19         db_table = 'contact'
  20 
  21 
  22 class Team(models.Model):
  23     """Model representing details of Team"""
  24 
  25     # Team Type Options
  26     CORE_TEAM = 'Core Team'
  27     CONTRIBUTOR = 'Contributor'
  28 
  29     TEAM_TYPE_OPTIONS = (
  30         (CORE_TEAM, CORE_TEAM),
  31         (CONTRIBUTOR, CONTRIBUTOR),
  32     )
  33 
  34     name = models.CharField(max_length=100)
  35     email = models.EmailField(max_length=70, null=True)
  36     description = models.TextField(null=True)
  37     headshot = models.ImageField(upload_to="headshots", null=True, blank=True)
  38     visible = models.BooleanField(default=True)
  39     github_url = models.CharField(max_length=200, null=True)
  40     linkedin_url = models.CharField(max_length=200, null=True)
  41     personal_website = models.CharField(max_length=200, null=True)
  42     background_image = models.ImageField(upload_to="bg-images", null=True, blank=True)
  43     team_type = models.CharField(choices=TEAM_TYPE_OPTIONS, max_length=50)
  44 
  45     def __unicode__(self):
  46         return self.name
  47 
  48     class Meta:
  49         app_label = 'web'
  50         db_table = 'teams'
  51
  [end of apps/web/models.py]
  [start of apps/web/migrations/0004_change_team_model_field_type.py]
  1 # -*- coding: utf-8 -*-
  2 # Generated by Django 1.10.2 on 2017-03-19 21:06
  3 from __future__ import unicode_literals
  4 
  5 from django.db import migrations, models
  6 
  7 
  8 class Migration(migrations.Migration):
  9 
  10     dependencies = [
  11         ('web', '0003_added_description_and_background_image_to_team_model'),
  12     ]
  13 
  14     operations = [
  15         migrations.AlterField(
  16             model_name='team',
  17             name='email',
  18             field=models.EmailField(max_length=70, null=True),
  19         ),
  20         migrations.AlterField(
  21             model_name='team',
  22             name='github_url',
  23             field=models.CharField(max_length=200, null=True),
  24         ),
  25         migrations.AlterField(
  26             model_name='team',
  27             name='linkedin_url',
  28             field=models.CharField(max_length=200, null=True),
  29         ),
  30         migrations.AlterField(
  31             model_name='team',
  32             name='personal_website',
  33             field=models.CharField(max_length=200, null=True),
  34         ),
  35     ]
  36
  [end of apps/web/migrations/0004_change_team_model_field_type.py]
  </code>
  
  I need you to solve this issue by generating a single patch file that I can apply directly to this repository using git apply. Please respond with a single patch file in the following format.
  <patch>
  diff --git a/file.py b/file.py
  --- a/file.py
  +++ b/file.py
  @@ -1,27 +1,35 @@
   def euclidean(a, b):
  -    while b:
  -        a, b = b, a % b
  -    return a
  +    if b == 0:
  +        return a
  +    return euclidean(b, a % b)
   
   
   def bresenham(x0, y0, x1, y1):
       points = []
       dx = abs(x1 - x0)
       dy = abs(y1 - y0)
  -    sx = 1 if x0 < x1 else -1
  -    sy = 1 if y0 < y1 else -1
  -    err = dx - dy
  +    x, y = x0, y0
  +    sx = -1 if x0 > x1 else 1
  +    sy = -1 if y0 > y1 else 1
   
  -    while True:
  -        points.append((x0, y0))
  -        if x0 == x1 and y0 == y1:
  -            break
  -        e2 = 2 * err
  -        if e2 > -dy:
  -            err -= dy
  -            x0 += sx
  -        if e2 < dx:
  -            err += dx
  -            y0 += sy
  +    if dx > dy:
  +        err = dx / 2.0
  +        while x != x1:
  +            points.append((x, y))
  +            err -= dy
  +            if err < 0:
  +                y += sy
  +                err += dx
  +            x += sx
  +    else:
  +        err = dy / 2.0
  +        while y != y1:
  +            points.append((x, y))
  +            err -= dx
  +            if err < 0:
  +                x += sx
  +                err += dy
  +            y += sy
  +
  +    points.append((x, y))
       return points
  
  </patch>
golden_diff: diff --git a/apps/web/migrations/0004_change_team_model_field_type.py b/apps/web/migrations/0004_change_team_model_field_type.py
  --- a/apps/web/migrations/0004_change_team_model_field_type.py
  +++ b/apps/web/migrations/0004_change_team_model_field_type.py
  @@ -1,5 +1,5 @@
   # -*- coding: utf-8 -*-
  -# Generated by Django 1.10.2 on 2017-03-19 21:06
  +# Generated by Django 1.10.2 on 2017-03-19 21:58
   from __future__ import unicode_literals
   
   from django.db import migrations, models
  @@ -15,21 +15,21 @@
           migrations.AlterField(
               model_name='team',
               name='email',
  -            field=models.EmailField(max_length=70, null=True),
  +            field=models.EmailField(blank=True, max_length=70, null=True),
           ),
           migrations.AlterField(
               model_name='team',
               name='github_url',
  -            field=models.CharField(max_length=200, null=True),
  +            field=models.CharField(blank=True, max_length=200, null=True),
           ),
           migrations.AlterField(
               model_name='team',
               name='linkedin_url',
  -            field=models.CharField(max_length=200, null=True),
  +            field=models.CharField(blank=True, max_length=200, null=True),
           ),
           migrations.AlterField(
               model_name='team',
               name='personal_website',
  -            field=models.CharField(max_length=200, null=True),
  +            field=models.CharField(blank=True, max_length=200, null=True),
           ),
       ]
  diff --git a/apps/web/models.py b/apps/web/models.py
  --- a/apps/web/models.py
  +++ b/apps/web/models.py
  @@ -32,13 +32,13 @@
       )
   
       name = models.CharField(max_length=100)
  -    email = models.EmailField(max_length=70, null=True)
  +    email = models.EmailField(max_length=70, null=True, blank=True)
       description = models.TextField(null=True)
       headshot = models.ImageField(upload_to="headshots", null=True, blank=True)
       visible = models.BooleanField(default=True)
  -    github_url = models.CharField(max_length=200, null=True)
  -    linkedin_url = models.CharField(max_length=200, null=True)
  -    personal_website = models.CharField(max_length=200, null=True)
  +    github_url = models.CharField(max_length=200, null=True, blank=True)
  +    linkedin_url = models.CharField(max_length=200, null=True, blank=True)
  +    personal_website = models.CharField(max_length=200, null=True, blank=True)
       background_image = models.ImageField(upload_to="bg-images", null=True, blank=True)
       team_type = models.CharField(choices=TEAM_TYPE_OPTIONS, max_length=50)
  
verification_info: {"golden_diff": "diff --git a/apps/web/migrations/0004_change_team_model_field_type.py b/apps/web/migrations/0004_change_team_model_field_type.py\n--- a/apps/web/migrations/0004_change_team_model_field_type.py\n+++ b/apps/web/migrations/0004_change_team_model_field_type.py\n@@ -1,5 +1,5 @@\n # -*- coding: utf-8 -*-\n-# Generated by Django 1.10.2 on 2017-03-19 21:06\n+# Generated by Django 1.10.2 on 2017-03-19 21:58\n from __future__ import unicode_literals\n \n from django.db import migrations, models\n@@ -15,21 +15,21 @@\n         migrations.AlterField(\n             model_name='team',\n             name='email',\n-            field=models.EmailField(max_length=70, null=True),\n+            field=models.EmailField(blank=True, max_length=70, null=True),\n         ),\n         migrations.AlterField(\n             model_name='team',\n             name='github_url',\n-            field=models.CharField(max_length=200, null=True),\n+            field=models.CharField(blank=True, max_length=200, null=True),\n         ),\n         migrations.AlterField(\n             model_name='team',\n             name='linkedin_url',\n-            field=models.CharField(max_length=200, null=True),\n+            field=models.CharField(blank=True, max_length=200, null=True),\n         ),\n         migrations.AlterField(\n             model_name='team',\n             name='personal_website',\n-            field=models.CharField(max_length=200, null=True),\n+            field=models.CharField(blank=True, max_length=200, null=True),\n         ),\n     ]\ndiff --git a/apps/web/models.py b/apps/web/models.py\n--- a/apps/web/models.py\n+++ b/apps/web/models.py\n@@ -32,13 +32,13 @@\n     )\n \n     name = models.CharField(max_length=100)\n-    email = models.EmailField(max_length=70, null=True)\n+    email = models.EmailField(max_length=70, null=True, blank=True)\n     description = models.TextField(null=True)\n     headshot = models.ImageField(upload_to=\"headshots\", null=True, blank=True)\n     visible = models.BooleanField(default=True)\n-    github_url = models.CharField(max_length=200, null=True)\n-    linkedin_url = models.CharField(max_length=200, null=True)\n-    personal_website = models.CharField(max_length=200, null=True)\n+    github_url = models.CharField(max_length=200, null=True, blank=True)\n+    linkedin_url = models.CharField(max_length=200, null=True, blank=True)\n+    personal_website = models.CharField(max_length=200, null=True, blank=True)\n     background_image = models.ImageField(upload_to=\"bg-images\", null=True, blank=True)\n     team_type = models.CharField(choices=TEAM_TYPE_OPTIONS, max_length=50)\n", "issue": "Add nullable attribute to the Team Model\nFollowing changes are required in the Team model: \r\n\r\n- [x] Convert the URLFields to CharField with URL\r\n\r\n- [x] Change the fields `email`, `github_url`, `linkedin_url`, `personal_website` to nullable fields\n", "before_files": [{"content": "from __future__ import unicode_literals\n\nfrom django.db import models\n\nfrom base.models import (TimeStampedModel, )\n\n\nclass Contact(TimeStampedModel):\n    \"\"\"Model representing details of User submitting queries.\"\"\"\n    name = models.CharField(max_length=100,)\n    email = models.EmailField(max_length=70,)\n    message = models.CharField(max_length=500,)\n\n    def __unicode__(self):\n        return \"%s: %s: %s\" % (self.name, self.email, self.message)\n\n    class Meta:\n        app_label = 'web'\n        db_table = 'contact'\n\n\nclass Team(models.Model):\n    \"\"\"Model representing details of Team\"\"\"\n\n    # Team Type Options\n    CORE_TEAM = 'Core Team'\n    CONTRIBUTOR = 'Contributor'\n\n    TEAM_TYPE_OPTIONS = (\n        (CORE_TEAM, CORE_TEAM),\n        (CONTRIBUTOR, CONTRIBUTOR),\n    )\n\n    name = models.CharField(max_length=100)\n    email = models.EmailField(max_length=70, null=True)\n    description = models.TextField(null=True)\n    headshot = models.ImageField(upload_to=\"headshots\", null=True, blank=True)\n    visible = models.BooleanField(default=True)\n    github_url = models.CharField(max_length=200, null=True)\n    linkedin_url = models.CharField(max_length=200, null=True)\n    personal_website = models.CharField(max_length=200, null=True)\n    background_image = models.ImageField(upload_to=\"bg-images\", null=True, blank=True)\n    team_type = models.CharField(choices=TEAM_TYPE_OPTIONS, max_length=50)\n\n    def __unicode__(self):\n        return self.name\n\n    class Meta:\n        app_label = 'web'\n        db_table = 'teams'\n", "path": "apps/web/models.py"}, {"content": "# -*- coding: utf-8 -*-\n# Generated by Django 1.10.2 on 2017-03-19 21:06\nfrom __future__ import unicode_literals\n\nfrom django.db import migrations, models\n\n\nclass Migration(migrations.Migration):\n\n    dependencies = [\n        ('web', '0003_added_description_and_background_image_to_team_model'),\n    ]\n\n    operations = [\n        migrations.AlterField(\n            model_name='team',\n            name='email',\n            field=models.EmailField(max_length=70, null=True),\n        ),\n        migrations.AlterField(\n            model_name='team',\n            name='github_url',\n            field=models.CharField(max_length=200, null=True),\n        ),\n        migrations.AlterField(\n            model_name='team',\n            name='linkedin_url',\n            field=models.CharField(max_length=200, null=True),\n        ),\n        migrations.AlterField(\n            model_name='team',\n            name='personal_website',\n            field=models.CharField(max_length=200, null=True),\n        ),\n    ]\n", "path": "apps/web/migrations/0004_change_team_model_field_type.py"}]}